First off and important: This is about dungeon content and not raids

I am getting into discussions with people saying to not use Selene, especially not to use Fey Light (skillspeed buff), because the addition to skillspeed will make TP users burn their TP faster.

Of course I understand that using more skills is draining more TP, but its not gone away into the air, it has acutally been used to deal more damage.

I feel like people are taking the gearing advice to not focus on speed and reflect it onto selene.

I know Selene can be trouble in longer bossfights, where you want to sustain a certain DPS/resource treshold for phases.

But leaving that situation aside, why would you be against Selenes buffs if Eos healing is not needed?
Please help me understand this, I'm perfectly willing to not activate it if it really is detrimental.