Well actually with increased skill speed going from 1000 to 0 is less attacks. Every 3 seconds you recover 60 tp. So if at 4 minutes you use all your tp then you just used 5800 tp (1000base + 4800[ 4min= 240secs ÷ 3 sec x 60tp per tick] excluding invig cause it doesn't affect the point I'm making) vs 4600 in only 3 minutes. Now if the monk sits there tp starved until 4 minutes then he did the same amount of attacks and damage and what was the point of using selene at all then.
the bard has to be willing to play paeon when needed to make it a dps increase or the boss/enemy needs to die before tp is depleted. Almost forgot, or use to help with a dps check/push a phase.

Long story short, your getting in more attacks in less time which means in that time you have gained less natural tp ticks, so less tp to use overall