IdoIdo
I agree, they should be int based, and a few thief skills and future bard skills should be worked into a mix of int and agil.
For example, make the songs increase another units str/int/agil whatever by a percentage of the bards int, say they 0.3 you're currently working with. That way the bard pumps out a solid buff of whatever stat a unit needs and makes use of what should become its own primary attribute.
Also, skills like dazing trap, steal, maybe even acid, should have multipliers based on int.
0.3 x int for acid, units sleep for a 5th of the thieves int, steal has a higher chance of better items based on int, or even agility since its about being nimble.
Working a few int based stat modifiers into the thief skills that seem based around things like bombs and traps makes sense to me.