All the guides your read to be the best lava bursting shaman you can be is always written from the standpoint on having BiS gear. So now little old me who do not raid like many of you is wondering with only LFR gear in mind. Which way should I go, haste or mastery? Is a bigger cap between them which to choose when the ilvl is lower or is it the same preference around that ilvl too?
the guides are made for BiS because at lower gear levels who cares? min maxing is pointless because simply playing the game and getting upgrades is better than perfecting crap gear.
if you don't have the legendary meta gem it's probably haste all the way, if you do just go for like haste = mastery roughly and that'll do, no reason to be stat perfect in LFR gear for a spec that has no real breakpoints or soft caps so just highest item level gear and avoiding crit is the key.