Well, they've since patched snipers. A select few can 1-shot you if you get hit in the upper body in close quarters. I've tested this by accident by running into a sniper around a corner (he had a bolt-action, I had 100% health).
There's always headshots as well :P
EDIT: Checked patch notes:

It's also worth noting that on hardcore mode servers, bolt action snipers will 1-hit-kill with a chest shot at any range.

As for assault being overpowered, I don't know if it was patched or not, but the F2000 was pretty OP back in the day (well, no, it just shot lots of bullets very fast, but was still more or less instant death.).
I'd rather they stop nerfing everything. The only weapon that's being irritating me lately is the AS-VAL when there's snipers using it. FAMAS is pretty fast at killing you, but hey, assault class should have an advantage over the others at close-to-mid range combat right?

f2000 is still pretty strong, little recoil, good accuracy, half a clip in a blink of an eye. no attachments and you can pwn tits with it.
had a similar thing with a sniper the other day aswell, ran through a doorway while a sniper was running out, was dead befor i could process that he was even there.

assault is pretty much the business at mid range, that is the point of them after all.
im still a UMP fan though, although i havent unlocked the mp5 yet