[WotLK] What setup have you found best for running heroics?

[Overtime]

I remember tank+4ret being a thing in retail, but what do you suggest?

[Zerga]

If you want to only PVE i would say you to use a mixed-class team. Long time ago i did Paladin/Warlock/Druid/Mage/Priest on WotLK and it's a very good composition, i did most of heroic dungeons.
Paladin is the most easiest tank for a multiboxer, Warlock have a tanking pet, Druid can heal and do high DPS, Mage can teleport/portals and have a Frostbolt and Priest is the best priest on WotLK.
I tried to do this team again on Lordearon but i'm too lazy so i think i'll make a 25 mans Raiding Team on Deathwing.

If you want to PVP too, I would say Paladin (prot when dungeon) + 4 Shamans or Paladin (holy when dungeon) + 4 DKs... But it's better to ask to my comrades about PVP since they have more experience that me on WotLK.

[Overtime]

I did DK pvp boxing in retail so that part is familiar.

[Jakkre]

I remember tank+4ret being a thing in retail, but what do you suggest?

Tank+4rets like u said.
By far the best setup for 5 man dungeons.
Ret palys kill trash mobs in a matter of seconds and ull hardly need a mana break because rets reggenerate their mana by using judgement.
The setup gets especially overpowered when u have the t10 two set bonus because it makes u able to spam divine storm which does insane aoe dmg and also heals the whole grp at the same time.
The healing that 4 ret palys provide with instant flash heal in combination with divine storm healing is more than enough to keep the tank and grp alive so u have basically 4 dps that do dmg and instant heals at the same time.
I have done all hc dungeons (including hor hc) with this setup.

As tank I would use a hybrid DK with 45 points in blood and 26 points in frost so u have abomination might which grants the team 10% more ap and icy talons which grants 20% haste.

Its also worth to mention that 1dk 4ret is the best pvp setup for 5 man boxing.

[kalvindeane]

Haven't tried it myself but I think Jakkre is correct on this.

DK + Ret has essentially no downtime. A lot of self healing and damage mitigation.