There are a few other things that could be done to make it a DPS increase, at least for certain jobs.

If added skill speed decreased the auto attack delay rather than increasing its potency, then it would be a pretty vital stat for ninjas, and maybe for monks. Also they could compensate for this by making your TP/MP regenerate based on your speed.

Adjusting the frequency of your non global cooldown moves, though, would probably be worse in the big picture. Certain party buffs and off global cooldown moves naturally line up so that burst phases are even larger when done as a party. However if one job needs more speed than another, then these phases no longer line up, and the whole thing falls apart, which will mean less party damage overall.