Speed should still lower the GCD, no? Also Ninja was a result of poor planning and (speculation here) wanting to be able to have gear that does not look the same as bard. I'm willing to bet their thought process was:

Ninja comes from thief
Thieves should use dexterity instead of strength
We don't want ninjas to look like bard
Let's pollute the loot pool with another unique melee set

They should have just put DEX on all the monk stuff and made them share. That's actually what they did with pre-ninja gear, but I guess they though it'd be OP for monk to get some free parry (lol). Then they made DEX no longer give parry so now it does literally nothing for monk and there's no excuse, but we're already too far down the rabbit hole.