In theory every single TP using class will run out of TP in a reasonable timeframe if they require constant uptime on target.

Thus, it is worthless if fights were like, 10-15 minutes of constant fighting.

Since they are not, we cannot conclude that skill speed is "worthless" but its pretty damn bad.

The other issue is "skill speed lets you get more attacks in for a cooldown". My take is it takes way too much skill speed, and you're better off with another stat.

The other main consideration is whether more skill speed will let monks (maybe dragoons too?) get another attack in inside their maintain rotation. I do not play either so don't know the breakpoints.

But the easy way to think about it is this: would you rather have all your offstats in skill speed? Or all your skill speed in another offstat?

And the answer to that question is easy. Thus, skillspeed is terrible. I won't say worthless, but its pretty bad.