My main is a tank, so whenever I'm dpsing a LFD pug, the first thing I look at with the tank is how they pull. You can tell a lot about a tank by how the pull. When they LoS, when the use what abilities, what mobs they hit first. A tank who pulls poorly (warriors who pull with taunt, for example) is probably going to have a harder time holding aggro, and a harder time dealing with bad situations, like when bad (skill-wise) dps pull threat by attacking the wrong mobs, using copious aoe where it shouldn't be used, and so forth. Bad pulling technique can lead to wipes, too... For example: the intersection in Halls of Stone. on our left: two casters and a melee, on our right, two melee and a caster. the DK tank (who's threat is bad relative to gear and who's spec is a little dodgy) deathgrips the one melee out of the 2 caster/1 melee pack. the casters start shooting at him, he doesn't LoS (plenty of room to LoS), and the second pack gets pulled into the fray. That's bad pulling. The good pull would be to Strangle one caster, DG the other, and use LoS to get out of the way and make sure the other pack doesn't pull.

I'll take low-level well-chosen gear from a good player over a bad player with good gear any day. Same goes for dps. I'd rather have 1.5k dps from a player who is playing well in crap gear, than 3k from an idiot who makes lots of major mistakes (Starfall pulling in adds, for example).