It depends.

If you overgear your tank, and are limited on threat redirection (Hunters, Rogues), it is possible to become threat capped. Generally, if I'm a tier or so above my tank, I have to manage my threat a lot. It depends on the quality of tank as well, but if I'm sporting 251s, and my tank is in 232/245 gear, there is definitely an issue of threat, especially on Paladin tanks.

As a Paladin tank, I have consistently found that DPS could beat me until I picked up my two-piece tier 10. Now my Hammer of the Righteous crits for 6k, making my threat generation significantly higher than when it was hitting for 3k. In a guild where you're all similarly geared, this kind of thing doesn't happen as much, but with PUGs (where gear levels can vary wildly) or new alts, this can be a serious issue.

Other cases where I have to manage threat:
1. Deathwhisper
2. Battle rezes, or other situations where a tank gets knocked out of the running for a bit.

I guess i was thinking of raid bosses, i can totally understand those two situations (deathwhisper and tank brez).

know in BC we could really pull aggro off a tank well into a fight, like phase 3 prince, so i was wondering if this still happens (in normal situations ie the dps not outgearing the tank by two tiers)

As stated above, it depends, but I find myself high on threat a lot of the time.

It's not as bad in ICC as it was in ToC, but it's still worse than it should be. Even with 2/2 Destructive Reach ( which got buffed while ToC was progression iirc ), I need to shatter at least once on most fights.

I love the damage that Kings gives me but now that I remember what Blessing of Salvation is called I may start asking for Salv again.

Blessing of Salvation is gone. There is still Hand of Salvation (http://www.wowhead.com/spell=1038/hand-of-salvation), which can help, but good luck having a Paladin who knows how to use it. (When Festergut was still Hard Shit, we wanted a DPS to use it to cool off threat from the recently-switched tank, and it took him 3 minutes and 4 people helping on vent to even find it.)

As a hunter pushing 8k-9k, on any non-movement oriented fight, I need to make use of all of my threat reduction techniques to not pull. That means two sets of misdirected shots at the start of the fight (via Readiness), constantly watching threat, especially around target swaps, etc.

Different tanks have different levels of success in keeping aggro, and good tanks will do better than poor tanks, but on raid bosses -- from Deathwhisper to Saurfang to Sindragosa -- watching threat, especially when working with less-geared tanks, is a huge part of my DPS role.

Of course, sometimes, you can't help the situation any. On one Deathwhisper 10 run, I poured out Misdirect onto the tank, flopped onto the floor, waited 10 seconds, and the tank still didn't have a solid lead. :/ Bad PUG tank iz bad.

But this is all hunter-specific. In short: Yes, DPS can pull, especially good DPS with bad tanks. Equal-geared equal-skilled tanks and DPS, the tank will almost always be quite a ways ahead.

Knowing how to use hand of salvation is one of the things that make good paladins great. I'm happy to be in the great category, mostly due to necessity when our resident thunder chicken is around, but still.

I run into threat issues pretty frequently. Maybe I run with crappy tanks, but Soulshatter gets hit once or twice any given fight.