I've always found it pretty well rounded. Could it be better? Sure. Its got 3 tons of fixed equipment (2xML and 2xCASE) which it doesn't have to have, but atleast there's a good reason for it, and atleast the equipment is useful. Its not the flashiest unit, but its a pretty solid design. Could the variants be improved? Sure, but then again, so could alot of `Mechs, and then we'd end up with lots and lots of clones.
Is the Prime some game breaking unit? No, but it fits in perfectly well with a lance, able to do just about anything from fire support, to watching out for pesky VTOLs, while still having firepower if someone tries to get in close.
The A is rather nice as well, though I have to admit, last time I used it, it was in a small, Solaris style arena, so I might be biased.
The B is perfectly serviceable as well. It can slip into an Archer's spot without too much of a loss in effectiveness (more missiles, less duration). Could it be better? Probably. But it still works out. Solid, but not flashy.
C and D are the obligatory C3Master and Slave variants. They're a little odd I'll grant you that.
E is interesting. A solid base unit for a c3i unit, which can keep firing until it is destroyed usually. Its also nice to have an ECM system to counteract anyone trying to cut off your c3i system. Has that nice obligatory ERPPC to let your spotter stay just out of ECM range and let you still be at short range.
The rest I haven't had a chance to use, but they look solid (But not always inspired).
Could it be better without fixed equipment? Sure. Does it lose too much? Not really. Is it going to be something I pick over everything else? Probably not. But its a solid workhorse design that I wouldn't mind having.