simming is not my thing and installing SimC and AMrR only made thing even more confusing for me.
I am a Destro Warlock.
SImC values Crit over Haste, but AMrR vaklues Hastes higher.
When I use the BiB option AMrR always sugegsts 4 pieces T19 LFR, lets me keep ilvl 900 head and legendary shoulders.
My other items in these slots are at least 25 ilvls higher.
So whom should I trust? SimC with crit and higher ilvl, or AMrR with haste and T19 lfr 4p bonus?
Things are about to change significantly, within a couple of weeks it should* be automagic for you.
However currently to get the best advice possible you need to make a custom gearing strat for your character. There are a few guides around to follow to make one, depending on your computers speed it could take a few hours.