I'm one who does actually learn what the fights do before I go. However, I do regular raiding in addition to LFRs on alts.
The last couple of months, since SoO came out, literally every single LFR I have joined, at least one of the two tanks says "tell me about this fight, I've never done it". THAT is annoying. Tanking, like it or not, is a special role that requires a bit of knowledge and leadership. Nothing more annoying than a tank in PvP gear asking for instructions every single pull.
I did flex before lfr every week when a new part came out this week, so I suppose one could say I researched the fights. As a dps I never prepare for lfr though, as tank/healer I skim through dungeon journal after the tank/healing icon.