Rolling chance to hit and damage together into one stat is silly and unbelievably stupid. Separate them or you tac combat will always suck.
I hate to say it because it's bandied around so much on this forum, but in this case you absolutely should have copy/pasted the core principles from, well, Age of Wonders, or Heroes of Might and Magic, or King's Bounty, or Master of Magic, or any other 4X I can think of right now, or every RPG that I can think of right now:
Attack = Chance to hit.
Damage = Damage dealt when an attack lands.
Defense = Chance to avoid getting hit.
Resistance = Chance to avoid getting hit by spells.
These are the freakin' amino acids of RPG tactical combat. You can derive all kinds of fun sub-mechanics from them... but, at the bare minimum, you need these four stats on every unit. Your combat will suck and make no sense without these basics.
Aside from ruining your mechanics and making your tac combat a laughable boring chore, leaving these out breaks the suspension of disbelief harder than sneaking a peek at the Christmas presents in your mom's closet and later having them given to you from "Santa."