Elemental oath is a bad reason. I have elemental oath up 100% of the time, no matter what. I can't remember any time when elemental oath wasn't active after the first cast.

Yes, the 18.5% crit is just whats on the character sheet, obviously with elemental oath and other talents its much higher than that.

Also as far as haste reducing mana efficiency, I never have mana issues anyway. Last, haste also effects the global cooldown which helps for burst such as FS->LvB

Anyway, not purposefully going for haste anyway its just what all the gear happens to have on it. And to whoever said 0.3 seconds off of a LB isn't that big of a deal, you're insane. .3s off a LB is HUGE - over the course of 20-30 casts you're looking at 6-9 seconds of extra casting which is ~4 extra lightning bolts which is what, 12000 extra damage - per shaman. I only gem for SP (unless I need hit) so the haste right now just seems to be appearing on all the shaman gear.