Oh man, I do.
That was definately the best thing that died with the LoM (i.e. I miss him).
For those who missed it:
There was this guy in shadowhaven who would summon any reasonable number of mobs of any reasonable level, on command, and there was a guard outside who would kill them if you ran away.
The upside: Parsing, something to do while lfg, FUN. The mobs spawned with a random model size and you could chose from a variety of mob types (models). Fighting a 50 foot tall gnome? AWESOME.
The downside (the balance): It wasn't really good xp.
In all the time I visited that guy I saw someone else there, maybe twice. So, even though the server population was much lower, it obviously wasn't keeping people from xping and it wasn't being used as an xp spot at all. Putting something like that back in the game could only benefit the server (and not just the players).