Couldn't agree -less- with most of the original points.
The sniper rifle sucks ass at anything but long range, you have no radar while aiming it, you completely give away exactly where you are each time you shoot it, and you only have four bullets at a time with a decent reload delay--that's enough balance. It is SUPPOSED to be super-powerful from far away, that's why sniper rifles were invented.

That is why teams fight for it, protect their sniper, call out the other team's sniper, etc. Adds great strategy and a whole other dimension to the game.
Plasma pistol combos can be really effective, but not ridiculously overpowered. It takes time to reach it's target (by the time it reaches you, you can have the often have the other guy dead with a pistol-pistol or even pistol-SMG combo) and is very possible to dodge.
The needler and brute shot are crap, I agree.
I have no idea what you mean by random grenade damage...seems perfectly consistent to me...
The sword is super powerful, yes, but I dont mind the unlimited usage. It's very possible to dodge or kill the guy from medium range or using even simple teamwork.
It seems like you want all the weapons to be equally powerful, and I don't think thats the idea. Different weapons have different strengths and weaknesses in different situations, with the Rocket Launcher and sword more powerful than the rest overall (thus they have the ability to turn the tide of a game).