A 3 man team could do most heroics if they're well geared.. or atleast if the Tank or Healer is.

I'm in the same boat, been dualing for a while and want to start doing Heroics with a 3 man team just cant decide on a team!

My Paladin tank is a no brainer (T8/9) but I have 4 other characters competing for the healer and DPS spots.

The way I look at, when you run a 5 man normally and 2 DPS die do you wipe? No (well not usually), only if the tank or healer dies. Or if your team is well geared and just want to farm badges, having 1 DPS doing 3k+ is not far off what 3 DPS did combined back in the early days of Wrath.