Aries

Aries has a plethora of uses. 
*Her most imporant skill is: she can't be knocked back or pulled.
**Against the Green Cube Boss, this means no more team-wiping roars.
**In the rift, she is an amazing solution to the stages that have 4+ adv/sk (granted she can survive, of course). This makes the rift stages 27/29/30 of rift 12 much easier (she needs rift reduction gear to pull this off).
** She is a better tank than most shield knights, along with Jin Andre.
*Her main skill does 50% and then bleeds for 480% of that (= 240%). This is a huge modifier for a main skill, 290%. Furthermore, every 6 attacks she does a 80%/10hit (= 800%) attack.
**Equipped with Root items, she actually has the highest potential for the Rift Corridor in damage.
**Even equipped with tank items, she has great damage potential.
P.S. Her MSPD is a little low.