Well, what if as an opponent we have a mage, whose spellcasting is delayed when he is hit. Then, the faster-attacking class would have an advantage against the mage even if it's balanced with the slower class according to your math.
Still its DPS so the fast guy could be more sensitive to magic (worse armour accesible). Higher DPS characters against environment- first all they can get for their money is caped. 2 nd for example poison can raise they death ratio against environment as their are naturally lower life pool.
I think that stun is interesting stuff. Excuse me that I will put it to the previous comment.
-sorry I cannot get to it untill Monday...