I'm at level 74 with my lates team (I now consider this my main team as I mained a dk in original wrath), unholy dk tank, disp priest, 3x frost mage. Have really been enjoying this group, just in with the DK dots and death and decay then blizzard spam with the mages. Haven't tried any of the wotlk dungeons yet, not for any particular reason just haven't ran past any while I've been questing. I have cleared nearly all the TBC dungeons with this team though, and will still do the odd one, have found Bot fun to run, can be cleared in about 25 minutes was my best time nets me about the same amount of xp while rested as questing so just do it to break up the questing. Collection quests have been killing me.

Teslah be very keen to see any videos you have I have a Timelapse of my main team doing bot if you want to see how terrible my set up is haha. Miss the old broadcasting style but mouse over has been an absolute godsend over clicking each window.

My other 2 teams are nearly level 71 just haven't been putting as much time and effort into them, I log them daily and try to get hellfire towers daily done, easy xp honor and gold, most of those teams are nearly full brutal now.

my current teams are
74 dk, priest, 3x mage
70 paladin, 4x shaman
70 feral, priest, 3x hunter
newest team as I'm keen to see what it would play like is holy paladin and 4x warlock, those are currently at 16 and will prob not rush to level them until I get some heirlooms

I have no big rush to get to 80, phase 1 doesn't interest me in the least I pushed hard when it originally came out to be apart of realm first Naxxramas and Malygos so will take this phase nice and easy. Ideally I only hope to be able to clear the ICC dungeons when they drop. My Tanks are my 'mains' so wouldn't mind focusing on one of those for each of the later phases.