Ok so when fighting Glubtok, at ~50% he teleports to the middle and starts hovering. When you kill the elementals that spawn they give 15 rep (increased by guild perks) per elemental killed with Horde or Ally factions (not tested on ally but I assume its the same). As long as you dont kill the boss and avoid the flame wall you can kill the elementals for huge rep.
You can also reset combat via death or any other combat dropping abilities and put a dif tabard on rinse repeat.
OLast thing make sure you keep at least a small dot on him, I used thunderclap which refreshed rend. Other wise he will despawn mid fight. Yes I said DESPAWN.
Tested in a group of 5 where I was a prot warrior (Victory Rush FTW) and everyone else just stayed dead, all 5 of us got Ambassador + Goblin rep maxed in less than 2 hours.
More than likely an exploit. (Also I have the title on the only character I care about so I figured instead of being a leecher I would share. Might want to do it soon not sure if blizz knows about it or not. Tested a week ago.
Searched , Heroic deadmines, Deadmines rep expliot, and didnt see anything similer.
EDIT: Average combat time was ~25mins, which was the time it took us to go from neutral / friendly to exalted.