While there is likely more to the story it could also just be that people in LFD are dicks. Case in point, I have a druid, I'm in 390 (healing) gear but decided to run dungeons for valor instead of LFR so I could gear up my feral set. Agi trinket drops and I roll need (there are no other leather wearers in the group) and a ret pally with two 390 trinkets rolls need as well and wins. Love those pallys that use agi gear right? Anyway, being the healer I let him die but the point is that people in LFD/LFR are usually just stupid and jerks and that is why you got kicked.