You're not getting it...1. Conserving MP = not damaging. BLM's aren't standing back there Auto-attacking. Therefore Melee DD's have an upper hand in keeping CONSTANT damage up. 2. While yes, Ballad helps, it REQUIRES having a Bard in the party to have it. It's not something a BLM can do to themselves to improve their own game. So yes, MP conservation is part of the game, but when talking raw damage, BLM needs to constantly Nuke to out DPS a traditional Melee and over a long battle, that gets harder and harder to do.
The 2 minutes thing: I was basing that on being able to keep constant nukes going ...like a DD can constantly DD. Without assuming you have a Bard in a Party. I understand it doesn't happen in practice due to reasons you mentioned (MP conservation/EMN) ...But that just proves my point. BLM has their limits already placed on them that forces their damage output to be lower than they potentially could dish out.
Monk and Warrior and Lancer can all do crazy damage too. It's just their individual auto attack and WS/combo numbers are smaller, but constant. The main issue is in order to compete with BLM damage, Melee need to be able to stay more or less stationary and not spend time running from AOE damage....that is NOT Black Mage's fault. That is a battle mechanic fault. Black Mages are usually getting higher damage numbers not because they are the most awesome DD, but because they aren't as affected by mob ranged attacks and can keep doing Damage. Again, not a Black Mage problem...battle design problem.
It's not that AF doesn't support decent damage...BLM isn't just about your potential damage, you get resisted ONCE, and it can mess up your whole spell set/Mana pool. It's the resists BLM's are trying to avoid by upgrading their gears.
Basically at the end of the day, instead of asking to nerf a class/job because it can out-damage your preferred job/class and/or is 'stacked' more often than your favorite, maybe instead spend time asking for more varied content/battles etc. that make different classes/jobs specalists for that fight. There is nothing wrong with the damage output blm has. It's spike damage...Monk, WAR,Dragoon ALL do good damage too, it's just steady damage.