I'll be more specific with what I meant before. Some of the things in this post is wrong or out dated, in my opinion. One example of out of date is someone was theory crafting still with Arcane Shots between Explosive Shots. They now work as magical dots and won't be clipped if you re-apply after the 2nd to last tick. An example of "Wrong" is the idea of Lich King enchants being better than Cata ones because of the agility. 22 agility is 44 AP and I believe .07% crit. More AP with different specs, but with survival, it's 24 agility for 48 AP, plus 10% AP = 53 AP? Roughly.
I don't recall what the 65 crit added as far as crit percentage, but it obviously applies more crit than the 22 agility does, even though crit doesn't scale multiplicative...ly. Reasoning behind the choice, I believe, is "per point, agility is worth more than crit. So go with an agility enchantment." But even a simulator says the difference is -34 DPS. Real world conditions would favor crit.
This isn't to say crit is better than agility, but we deprive ourselves of crit options with gems. Yellow slot +10 agility bonus? Break it for more agility. So having a crit enchant on cloak balances that out. As far as the 20 Agility to glove vs. 50 haste. That's a different story. Haste stacks mutliplicatively. (apparently not a word) The 50 rating stretches farther. Another point is a secret I'd rather not share.
But I got an infraction from my previous post being to vague. Now I've given some examples. New to the forums, so yeah. Sue me. :[