Usually you WANT to act first in a turn based game, because this way you can hinder, damage or even kill your enemy before he can even react.
We already act first in a turn, acting last is a tactical precious position. Especially since very few fights in this game only last 1 turn.... and DoT effects only apply and count down when a turn is starting. This means dispelling (or countering them with regen healing) before the turn ends saves you from a lot of damage.
