You can gem however you please and whatever your preference is, given it's within reason (healing stats) and you can get the socket bonus
Crit = 10m King?
Haste is an irrelevant stat until the threshold ticks are fixed and HTT/HST work properly.
Now, I have another question. If they correct the HTT/HST haste threshold in 5.2. Because haste is our worse throughput stat because it makes us consume too much mana with not enough mana return, in 10m could it become ideal to stack crit after attaining a comfortable haste breakpoint? For the resergence mana return?