Game Basics (Mechanics/etc)

This section will cover some information related to game mechanics that can be useful for starting players to know about. (Information is not whole yet, I will update as I progress further along the game and have more time testing, if something is wrong do forgive me :P)
Honor Gain per Battle: If you are 6 levels below the npc force, then you will gain double honor from that battle. If you live in city that your nation owns, you will gain another x1.2 honor. Then there is rebuking, which will multiply the honor gained by 1% per level, and lastly there is apollo ritual which is another multiplier to the honor gained.
Formations: Each formation level increases that respective stat by 1%. So lv 20 BD form adds 20% crit, lv 20 BU2 form reduces damage by another 20% (so final damage = 80% of what you were suppose to take). lv 20 W/T/TU form on the other hand increases the common/strategy/skill attack damage dealt by 20% (so x1.2 of what you would've dealt, not sure how it affects hybrid heroes). Assuming you are equally geared/leveled/etc, it is almost always better to use DEF/Dodge form over W/T/TU (i.e. if you fought yourself, one using say W form while the other using DEF form, the one in W-form would be doing 1.2 * .8 = 96% of original damage to the heroes in def form, however, the heroes in DEF form would be doing 100% of the original damage to the guys in W form).
Parry/Dodge/Counterattack: All increases to parry/dodge/counterattack from any source is additive (so if you have parry form lv 20 and using a parry unit with 10% parry chance and orange def totem with +15 parry, that unit has a 45% chance to parry). Dodge works on both skill/normal attacks and simply avoids that attack. Parry works only against normal attack but will allow a unit to avoid the damage and sometimes (depending on the unit parrying) return damage to attacker instead. Counterattack can activate when you are hit, the difference here is that the unit launches an attack instead (i.e. if a firebull parries, he just returns damage to 1 unit, but if that firebull counterattacks, he will launch an attack and deal damage to all enemy units as usual). Warlocks cannot counterattack, they can parry, but will not return damage.
Crit/Hit/Toughness: All increases to crit/hit/toughness from any source is additive as well. In this game, Crits are rolled BEFORE dodge/parry/counterattack, so if you crit, the enemy cannot parry/dodge/counterattack. Hit only affects dodge and will not work on parry (or so I believe). While toughness is used to counter crit. Lastly, when a unit crits, the damage will be multiplied by x1.5.
*Exceptions to above: Anytime trigrams & research grant dodge/hit/crit/toughness, they are all multiplicative with however many total dodge you had before. Let's say you have 20% dodge from research, and 5% dodge from trigram on your firebull unit in W-form. In this example, your firebull will still have 0% chance to dodge (0 * 1.25 = 0); if you put that firebull in lv 20 Dodge form, he will then have 25% dodge chance (20% * 1.25 = 25%). As for hit/toughness from research/trigram, I believe they simply negate the dodge/crit multipliers from research/trigram. **Note this is only talking about research & trigram, there are other sources of dodge/hit/crit outside of formations which are additive (i.e Kaga, Neeshan, Monroe, totem, and lastly innate dodge ability from units such as Calvary). 
Healing Formulas: Heals Round Down (meaning if you heal 114.6, it will heal 114). Int does not affect Success Rate. Troop count remaining does not affect heal. Healing is not considered damage, so things like Strat attack damage glyph will not increase it (strat att form & strat att glyph still affects it because those affect total strat attack). From past posts that I've read, Strat form will increase total healing done by a fixed amount of 33% at lvl 20, but from current tests, lv 20 strat form increases healing by 40% (so they may have buffed it). 
Supplies (Marlord): Force Level * 1.6 + 30 + Total Strat Attack/6 
Medical Corps (whattoc/chansona): Force lvl * 2 + 40 + Total Strat Attack/5
Surgeon Corps (moonsong): Will test after I get there...
Healer (Neilhence/Gamzrin): Will Test if i get there....
Note* Healing also scales indirectly with how well you can decrease enemy damage (thru stuns, dodge/parry, applying damage debuffs, and dealing damage to enemy lowering their troop count).
Damage Formulas: Resilience does not affect damage dealt/taken. If unit deals hybrid damage (ie Skill&Normal for seema's sky wind) then both skill attack & common attack as well as str/dex will boost that skill's damage (Both skill/common DEF and str/dex will be used in calculation for protection against that damage as well). For any skill attacks, every 100 morale will increase damage of skill attack by 100% (so a skill attack launched at 300 morale will do x3 damage than it would than when launched at 100). Damage Dealt/Received is relative to their own type and the units in question, a horse for example gains alot more skill att per level than a book would give strat attack per level, but this does not mean that skill attacks deal that much more damage than a strat attacker would.
Note* Damage formula isn't really useful for anything since there are too many attackers and the exact formula is different for different attackers just like heals are for different type of healers, also there is no data on NPC stats and what mods they've got so knowing your own damage output won't do any good. But if you are interested, read on!
Here are what I can tell to be the case:
*A base attack damage value exists for every unit just like healers, you can have 0 common attack and force 1-I and still do 30 something fixed damage with your starting heroes & drafts due to this initial base damage. Meaning the damage formula is something like: (Base Damage + Effect from stat & att) * Global multipliers 
*Str/Dex/Int adjusts the output of your ATT and DEF. The bigger ATT&DEF you have from gear/etc the more effect you get out of having higher str/dex/int. Force level is pretty much irrelevant here, meaning as long as the attacking unit has a constant amount of attack (i.e stay at 1000 normal damage) and the defending unit has constant normal def (ie 700 normal def), then the unit's normal damage will only be affected by so much for every str change (i.e. if unit gets 30 damage increase per 20 str at force level 1, it will get that same damage increase per 20 str up at force level 100 so long as the ATT of unit and the DEF of defender stays constant). The greater the difference in ATT of attacking unit and DEF of defending unit, the greater the difference stats will make. 
*Force Levels gains grants a damage multiplier to damage dealt&taken by that unit. For example, if lets say every force level gave a unit 1% more damage, then someone with 10 force levels higher will do 10% more damage (so say at force 1 the unit deals 100, then at force 11 the unit might deal 110 damage, this can be represented in formula like this: Damage Dealt * (100 + attacker force level - defender force level)/100). This is only an example, hard to tell whether or not there is diminishing returns or if different units have differing force level effects, but it is definitely a global damage multiplier. 
*Fylgja glyphs that affect ATT/DEF (meaning life strat attack glyph and not strat attack damage glyph) directly boosts the relative ATT/DEF by that glyphs indicated amount to all units on the formation. So when you use a healer and you've got a primary strat attack glyph, that healer's heal will come out exactly as if he had 4% increased strategy attack. 
*Damage calculations of each type (Normal/Skill/Strat) are done separately and then multiplied by global damage multipliers at the end. Meaning for example take Seemacshee's Sky wind. The game will calculate the Normal Attack damage part of it with normal damage related stats (str/normal def/etc), and then it will calculate the damage derived from the skill portion. Then finally any global damage buffs (i.e Monroe damage boost, Crit damage boost if crit, etc will be multiplied onto the final summed damage). 
*Lowering troops by 1% of their max life will reduce their damage by .5% (so if you thorned an enemy for 20% of their hp they will be doing 90% of what they would do at full health). The exception to this is units like God Dinwye that deal more damage the lower their troops get.
*Damage Values do fluctuate by at least 10%-15%. Meaning a hero's damage is not always constant, there is a range (pulled by some RNG value) of at least 10%-15% per hit. So like if on average your hero at max health deals 100, his damage may range from 95-105 or about there.
*Immunity tech decreases the final damage taken by a percentage per level. Hard to test by how much since I need immunity to beat thru the zones, can't just level it from like 1 to 20 in one shot and observe the difference. If I had to take a guess, it might be .5% per level.
*If your attack would do no damage, damage instead is set to a minimum of 1.
From these observations listed above, this is my guess on the damage calculation done by game (The numbers may be different, but the format probably looks something like this): 
Final Damage Dealt = (Base Attacking Value + Total Attacking Value - Total Defending Value) * [(Q + attacker force level - defender force level) / Q] * Other Global multipliers * Damage Range Fluctuation
Total Attacking Value = (X + Attacker's str) / X * Total Common Attack / R
Total Defending Value = (Y + Defender's str) / Y * Total common defense / S
Base Attacking Value = a fixed integer like 30, 31, 32...etc. 
Variables X, Y, R, S, Q are just integers. R & S will depend on the unit that is attacking/defending. And Variables X & Y signify how much efficiency Str will boost the Common attack or defense. Q adjusts how much effect force level has on damage. For a regular unit like jurica, firebull (meaning unit type with no high damage, etc), a R&S value of 2, and a value of 200 for X & Y along with plugging in these values with correct global damage multipliers has given me a fair amount of relatively accurate damage displays when testing with firebulls vs drummers and having their force levels same. The R & S values will also be different for skill & strat attack. 
Global multipliers is things like unit Buffs (ie Monroe), formation increases, Increase damage effects from Force Upgrade, and any other damage modifiers such as from a Primary Normal Attack Damage Glyph, damage fluctuation from RNG and damage adjustment from % remaining troops at the time of attack, etc. 
An example calculation is for example take your firebull (200 str), and lets say it has a combined total of 3000 normal attack from research, weapon, fylgja, and you are using primary normal attack glyph (so total 3120 normal attack) and it is attacking say an enemy drummer (100str), and that drummer has lets say equal force levels to your bull and 1500 total normal def + a primary normal def glyph and immunity tech of lv 50 (so total 1560 Ndef and 25% worth of damage immunity assuming it is .5% per level of immunity). The bull at full health will deal approximately: (30 + [(200 + 200)/ 200 * 3120 / 2] - [(200 + 100)/ 200 * 1560 / 2]) * .75 = 1485 damage to the drummer 
Once again, the R & S values (and X & Y values) will be different depending on the unit and attack type, but the damage formula should be something like this. Anyways, the most important thing to take away here with regards to understanding damage, is what i've italicized and underlined in the text above. Another Important thing to take away is that if you had to choose between an ATT glyph vs an ATT DMG glyph, the ATT glyph will be better 
Unit Draft Cost: Higher draft cost does not necessarily mean a unit is better. Draft cost is simply rated by troop gain per force level (which you can tell by look at the starting troop count at lv 1). The higher the troop gain per force level of that hero, then the higher the draft cost of that hero.