One of the rumored changes to Skill Speed coming in Heavensward is that it may end up changing the amount of TP recovered per tick.
Check how much skill speed you have on your gear. Even with a base GCD of 2.5, every DoW class runs at a TP deficit. Skill Speed and other attack speed buffs just makes the Deficit worse because you are still recovering the same amount of TP every 3 seconds while at the same time spending more TP per second.
