You could, like someone suggested, simply do nothing during the haste to "simulate" lower haste. But...like...what is the point of the haste buff then...?

Essentially, what it boils down to is, if you ever run out of TP, skill speed is utterly worthless to you, unless it facilitates some mechanical timer sync (such as maybe going through your buff rotations tighter). So at best it does...nothing. This includes static skill speed.

The simplest explanation I can give for those that doubt the math is...

1. Everyone starts with 1000 TP.
2. Everyone regens TP at the same speed.
3. At any given time the maximum amount of TP you can spend is 1000+TP/sec
4. Once you "run out of TP", regardless of how fast you've run out of TP (whether it took 1 sec or 1000 sec), your total TP consumption is 1000+TP/sec
5. At this point, your damage is (1000+TP/sec)*(DPTP, or TP efficiency)
6. Therefore your damage done is dependent only on TP efficiency, NOT dps or haste.

I also want to clarify I'm not advocating whether Fey Light or not is "better". I'm simply clarifying that it is definitely possible to lose dps with more haste, if you end up using lower TP efficient abilities.

Guys if you remember...this is literally the main reason monks/dragoons etc. of old stopped using Fracture and Impulse Drive...while a technical dps increase it simply wasn't efficient enough to use.