>>715044282I think the original idea was that you would spend more TP for stronger abilities like a burst window and then resort to lower cost TP abilities to conserve it. Except that never really worked and most abilities had a flat TP cost except for AoE ones.
At some point, it was just decided that TP as it currently was didn't add anything to the game and it had been a mostly unused mechanic for so long that there was no reason to go back and retool it into something useful, so it was just removed. In theory, TP could've been better implemented to move classes away from rotations and cooldown centered gameplay to more flexible resource generation/spending designs, but since everyone was used to the former, it was more hassle than it was worth.