For me, rockets on a mech just don't work.... but I go for the long game, and I tend to go for fast lighter mechs, or fire support anyways.
I will admit, I've been on the receiving end of several of the rocket mechs --- the Catapult and Marauder come to mind.... and I've had a pristine Bushwacker killed in one salvo from the Catapult (which promptly shut down from heat, allowing it to catch 3 gauss and a Heavy PPC to the CT in the next turn) --- but during another battle, the Marauder attacked a King Crab, and while it sanded off most of the armor, also left itself shut down at range 4 with that same King Crab, which was the WOB version with the twin Heavy PPC's and C3i, which meant it got tore up as well..... and failed to kill it's target.
Rockets on fast vehicles seem to work, as well as on little mechs that can dash in, use them, and then kind of dance around, either as an initiative sink, or popping with a medium laser as an annoyance factor.... but the bigger mechs, while scary, end up being an all or nothing approach.
It's worse when someone TAC's a rocket launcher that's still loaded.... I've seen that chain reaction happen once....and it wasn't pretty.
Nahuris