Why Do Mana Users Have To Manage Their Resource?

[DumdogsWorld]

TP users always were able to go through their rotations without looking at the TP bar.

If you actually manage to run out of TP, you are doing something very, very wrong.

I'm curious as to how you AOE as a DRG. Nobody ever uses Goad on me, and I can only use Invigorate so often...