Post by Timmeh
Just a very rough idea (off the top of my head before someone starts moaning that they did blah blah dps with blah blah stat) of what you will need to perform well in the zones listed. You can most likely survive with less, but rely somewhat on other group members to carry you:
Heroics/Naxx 10/Sarth 10+25 with 0 drakes:
Tanks:
540 defense is mandatory
23k health is an absolute minimum for an off tank, at least 24k is preferred.
combined dodge and parry of around 30% (a bit lower isn't a massive problem).
DPS:
As close to the yellow hit cap as possible (see
http://www.wowhead.com/?forums&topic=56336 for the caps), being on it, while ideal is certainly not essential.
2.5k AP
20% crit
Naxx 25/Malygos 10+25/Sarth 10 + 25 with 1 or more drakes
Tanks
540 defense is still very much mandatory
28k health
30% dodge + parry
Hit and expertise are nice to have, but not realistically worth stacking (see the caps page if you really do care, though).
Shield block value and shield block rating - also nice to have, but you'll likely have enough at this stage of instancing without worrying about it.
DPS
Yellow hit cap (see above)
Dodge expertise cap, or as close as you can get, being a bit off isn't the end of the world.
3K AP, closer to 3.5 if possible.
30% crit.
As I said, should be enough to give people a rough idea, as long as you're pretty close you should be okay.