I've said it in this forum and even on blizzards that I've asked for NPC vengenance. So that as our gear gains the amount of damage we do to the mob increases his damage output to us. Think this would at least slow down how some 5 mans get pulled. Don't get me wrong though. After a time, yes you are sick of doing a certain 5 man and you want to make it fast. But, and I forget what xpac it was, that blizzard basically had all the tier gear on vendors and your 5 mans provided you the points to buy such gear. Sure if you put the LFR tier on vendors like that and make 5 mans heroics actually heroic I wouldn't mind that but I know your "hardcore" people would have issues because they would be forced to do the content for at least the first raid tier to get better gear to assist in raiding. Technically they already have to do that anyways but they will gripe just to be heard.