I'm definitely not a professional but I have been manually boxing ever since they disallowed software and hardware boxing solutions, but I figured I'd comment to get a conversation started (there aren't many of us left!).

For WOTLK:

The classic Paladin, 4x Shaman setup has gotten me the best results for pushing "harder" content (titan rune beta heroics). I've also had a lot of success with Paladin, 3x Boomkin, RSham. This squad obliterates regular heroics with the massive starfall/hurricane combo. I've also run Paladin, 3x Demo Lock, Disc Priest which has very high sustained AOE dps, but the Felguards die more to AOE and cleave than I like and I prefer smooth runs without having to deal with resummoning pets. I have a Paladin, 3x Spriest, RSham team that I'm working on (2 priests are level 76 and one is 80). In theory I thought this would be fun to play with all of the self-healing the Spriests do, but managing their dots is annoying to have to do now that everything is manual.

FOR Cata:

In Cata I plan to run the Paladin 4x Shaman team primarily, with one of them being Resto (may swap for a different healer). Having 3x earthquake with the knockdown effect (that doesn't DR, but can only happen once per mob per cast) sounds strong. Being able to unintentionally disrupt caster mobs in heroics has a lot of RNG attached to it, but it sounds like it could be fun.

Just to see how it goes, I also would like to try out Paladin 4x Disc Priest. I'm not sure what the damage of a Disc Priest looks like in Cata, but if I can manage to get half the dps of an actual damage dealer on each priest, it'd basically feel like running dungeons with 2 dps, but with the safety of them all being able to heal (and shield themselves, which might be useful on movement-heavy fights). Smite dps with Atonement means constant heals going out, and I can supplement with true heals from the priests' big healing toolkit. If it's bad, Spriest has some great single target dps in Cata from what I've read, so I can always dual spec shadow.

With the changes to Hunters (using focus instead of mana, trap launcher, auto-shot while running), I'm considering bringing up my level 70 hunter squad for Cata. Having to swap aspects for mana right now feels annoying, and having to run into melee to explosive trap (or miss out on the dps) is also annoying. These two problems go away with Cata (trap launcher coming in WOTLK phase 4 ).

Curious to hear what others are currently running or planning to run!