I gave it much thought and I have both a complaint and suggestion regarding ability balancing for end game.
How often have you been playing a character who has an amazing direct-damage ability, only to have it dwarfed end-game making your character completely useless while a general overpowered and unkillable?
Well the problem is: If I have a direct damage spell do say 1000 damage. That is great at beginning game, but near end-game my character usually deals a good 3-5 hundred damage a swing. By the time I get a single ability shot off I could probably get 3-4 swings of my weapon in. This means that the ability is useless. This problem makes the generals overpowered as they have high melee damage + priest healers + high hp + their abilities like the oak's invulnerability and the vampire lord's hp regeneration and teleportation (damage but more importantly prevents enemies from running) and stun.
Characters with stun abilities begin to become superior to those with damage abilities. All someone has to do is get enough HP as a general to not be insta-killed and let the priests you summon heal you.
My suggestion: Get rid of +weapon damage items completely. Anything that does + weapon damage including abilities like god strength for the rook. Instead replace them with + damage. + damage will increase ALL damage dealt, ability AND weapon. Of course the bonuses should not be +100%, maybe a +30% instead? What this would mean is that as a character scales his strength using items, the abilities would scale as well so at end game my fireball or snipe skill is not 100% useless. Also add + effect items, like +30% effect, so durations of abilities like invulnerability increase, stun increases, and so on. And of course add effect resistances, which are the counter to + effect items so -30% enemy ability effect aura (does not stack).
I would also hope that the ability text would scale as well as the actual ability damage/effect as it would be very valuable to the player to know what the abilities do exactly.