Reduce Grenadier dmg vs. heavy from 50% -> 35%

Grenadier is a wee bit too powerful vs. everything. 
This will keep its value vs. heavy armor still very high, but not OP like it is for the cost. 
(Grenadier will still have highest DPS vs. heavy as a function of cost, after this nerf).
Merge pull request #5413 from psydev/patch-1

Reduce Grenadier dmg vs. heavy from 50% -> 35%