Right now Oak seems to be the only balanced demi to me. The main part of every single one of his abilities is %based or a flat effect and thus usable throughout the game regardless of level and equipment (not entirely but far more than straight number abilities).
What i'm trying to say is that other characters abilities that do damage etc. i.e. The spit and life steal abilities for UB, Snipe/Mines for Regulus etc. dont scale well.
Snipe would be far better late game if it was:
lvl 1: deals 150-300% of weapon damage depending on range (more damage @ longer range)
lvl 2: deals 200-400% of weapon damage depending on range
lvl 3: deals 250-500% of weapon damage depending on range
lvl 4: deals 300-600% of weapon damage depending on range
lvl 5: the current stun passive at the end of the snipe line.
If abilities ignored armor for all % of weapon damage based abilities then lvl 4 snipe could deal upwards of 2k damage on a retreating foe. Making it the finisher it is supposed to be, as it is snipe is pretty useless once lvl 17+ is reached, same for other abilities.
Mines could do
lvl 1: 100% of weapon damage
lvl2: 200% of weapon damage
lvl3: 400% of weapon damage
lvl4: 3x400% of weapon damage +30% slow
With items are they are at the moment; offensive capability is too low and defensive too high when the game degenerates into an autoattack fest with lifestealing for great justice. Other than stuns oak is the only character with abilities that can turn the tide of a battle at that point; his sheild, buff, debuff and ocassionally even last stand are incredible even at lvl 25 with uber items.
Diminishing returns on stuns, wow style, would be a good thing. Something like every time you are stunned, for the next 30 seconds it upgrades your (hidden) immunity rank. Rank 0 - Full stun time, Rank 1 - Half stun time Rank 2 - Quater Stun time Rank 3 - Full time but 50% movement + attack speed instead of stun Rank 4 - Half time, 50% movement + attack speed Rank 5 - No effect.
Each stun would reset the 30 second timer.
Just some ideas i thought i'd throw out there