I currently do 140-160K on LFR (ret paladin who I retired in preparation for WoD), depending on the boss and on whether i'm helping in the fight mechanics. I achieve about the same on Flex (if and when we down a boss, which often is just the first one. pugs...), but I often see players doing below 80K in there for some reason. I don't know if that's enough or even feasible, given that my weapon isn't perfect and my trinkets are ToT LFR ones.