No, people want blm nerfed because they make endgame trivial, and because they isolate non-blm's out of some events. While technically, yes, you can do DM without blm's, it takes a very long time to get people for it, and you actually have to put some effort into the fight. Make a strategy, keep everyone alive for the fight, work on killing each AA individually; that's what SE wanted people to do, not just show up, cast a spell and win. The blm-only method exludes other jobs from being able to try, and since a lot of people only want to do it via manaburning, it makes it that much harder for non-blm's to get things done.
Again, exp is irrelevant in terms of nerfing, although I am glad someone(you, specifically) finally brought up something other than monk cannon's exp rates. Chi Blast is strong, but it also has a limiting factor in that we can only do it every 3 minutes, and that we have to constantly boost to get it that strong. There's also a limit in that Chi Blast can be resisted significantly. A monk can't just toss out a ton of Chi Blasts all at once or keep using them to "nuke" down whatever they're fighting, so we're already fairly balanced for endgame fights. During those 3 minutes we're cooling down Chi Blast, the NM is healing their hp so you can't just mass Chi Blast a win.