My best friend and I have just started running 2 man HMs this week. I'm a shadow tank and he's a gunslinger DPS. We are both 124ish daily commendation / reward geared with companions that are the same. Mostly, I run a healer companion and he runs a ranged DPS companion, although we have used everything from healer / healer to ranged DPS / melee DPS companion combinations depending on the boss. So far we've tried and completed all the bosses in the Esseles and Kaon. The only thing we haven't been able to do is the bonus boss in Kaon...90% of the time my healer seems to bug during the add phase, he turns off and his entire quick bar goes grey. I love love love the companion system. And I love that is possible to run HMs with only two people and that it's possible to progress to that point with two people in the same way a 4 man group would by doing dailies, heroic dailies and regular 50s. It's fun, it's challenging and has quickly become my favorite thing to do in the game. Thank you Bioware for giving us a way to play at an extremely high level in a very small group!