Well, it's not related to skill speed at all, but on BLM, Selene fairly frequently causes my AOE rotation to break down. The spell speed bonus, on top of the huge amounts on my gear (thanks, Ironworks!) actually causes problems with the mana ticks we get back from Umbral Ice.

As far as skill speed goes, in 4 man content I don't really think that's as big a problem. You have frequent breaks between fights for TP regeneration, and boss fights in dungeons typically have enough "go do this other thing" mechanics that your TP doesn't really go down to a dangerous amount.