As handy as these mods in WoW are I've come to think of them more as a crutch. In older MMOs your dps and threat and such you had to keep track of yourself...it showed a bit of skill if you could maximize your dps while maintaining a threat low enough not to gain aggro and if you miscalculated it led some pretty fun and exciting times as your tank and healers scramble to try to keep you alive. Same with DBM...that just completely removed any skill that was needed.
And then there are the times when your Cleric got aggro and the tank and other off tanks aren't paying attention to chat so you Manaburn to get aggro sacrificing yourself to save a group wipe. Ah, good memories :)
Personally I wouldn't object to a DPS meter in game, but if they have logging good enough to support an external ACT-like program I'll be happy. I like having ways to actually test the effectiveness of different fighting combos and gear a bit more objectively.
As for having a "threat meter", I've used them and I would probably use one if it was present. That said, I think I'd prefer to not have one since it does make things easier.