I have still yet to really see a good argument for keeping Heroic dungeons in this thread TBH, and it seems most people here are very ambivalent to their existence. Where people say that they "fulfill a function", are they not just solving a problem that only exist so that HC dungeons can justify themselves (IE: The iLvL difference between Normal and M0/LFR)?
The main argument I see is that they are a very early gearing source - the final pieces of gear you get before M0 and LFR - but is there a reason Normal cannot fulfill this function? Before level scaling it made sense so we did not have to get all our gear from 4 max level normals but is there any reason why iLvLs cannot be "normalized" around a "Max level Normal -> LFR/M0" progression? Surely this just means there is a lower difference in gear between normal dungeons and LFR/M0, and do anyone actually lose out from this? It helps out, if only a little bit, with iLvL inflation and it reduces the (somewhat perceived) barrier of entry between normal dungeons/leveling content and endgame. WoW has a general problem with needing you to understand and do too many different things as part of playing it, Heroic dungeons seem to me to be dead weight at the moment.
I generally agree with the "don't remove content just because some people don't care about it" argument but in this particular case it seems to me a benefit (if only a minor) to actually remove the content since the issue of "more difficult dungeons" is generally solved by M+ anyways.