The Roc 3 is surprisingly potent. It's the cheapest unit in the Clan arsenal to carry a Medium Pulse Laser, and the lack of jump jets isn't that huge a deal since it keeps that respectable 5/8 movement profile. The armor drop is a bit of a pain, but really not all that bad. It still has enough to take at least 2 ER Medium hits, possibly more. I think how wantec used it is the ideal; using them in urban terrain looks like it could work, but then you either:
-End up not needing the pulse bonus more often than not, or,
-Bemoan the lack of jump jets in order to keep up with other targets.
Having an MPL in the main gun is probably one of the few situations where I like them. Main Gun hits are rare enough to not matter in most games, but arm hits are another matter. In this case, losing an arm isn't too bad - the pulse bonus and lost arm penalty will end up cancelling each other out. Meanwhile, the effective 360 degree coverage means that it won't be outmaneuvered by the lighter targets it excels at taking down. I like it.