really depends on your group make up. Last night i was using a Commando and Sage which both have decent CC, the Sage having the longer CCs, and both can heal. Sage also has a tank companion. I was able to do all of the heroics on Coruscant and then most of the ones i was able to get on Taris.
However, from what i hear the difficulty scales drastically after 25 in terms of the heroics, so im unsure 2 box + 2 companions can do it.
Also, current state of Flashpoints only Esseles which is the first flashpoint is truely dual box able with only 2 toons, as stated in the last patch notes Hammer Station had a lot of bugs and was overly difficult at 18 2 betas ago, and i wasnt able to get in there with a normal group to test it again. I do believe that most of the flashpoints will require 4 players rather than companions. So this is also food for thought if you wish to run your own flashpoints you might as well run 4 toons.
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