Size/Weapon glitch doesn't always work. I can't do it on my PS3. I know some people can, that's nice, but it's an inconsistent glitch, not one that everyone can use reliably. on't try and argue otherwise until you've played every copy of the game on every system it can run on.
Your Rhett build when I use it has trouble hitting the walls of a building when I'm INSIDE. CARB-9 build is pretty good, but I can only go through 2 - 3 people if I'm lucky before reloading - with my Galactic it's a bad run when I need to reload before downing my 4th target. I know people who swear the Sea Eagle is OP compared to the MP.
ANY WEAPON CHOICES ARE BASED ON PERSONAL PREFERENCE. I can't beat this into people's heads enough, apparently. YOUR "perfect weapon" will be a waste of space in someone else's hands. Theirs will be barely usable in yours.
I don't think the skills you listed are OP, so much as some of the others seem underpowered. Only real example I can think of is the Medic speed boost - I can't come up with a way to make it as valuable as the cost would imply. Pretty much everything else is situationally effective, but requires proper use to be truly effective.
Adrenaline has a long cooldown, and doesn't prevent you taking damage at all, it still counts the hits, they just don't apply immediately - it has its uses, but there's ways around it too. A couple of good hits then avoid the guy with the buff, for one. Just straight stayong away from him until it wears off will work too.
EDIT: I wouldn't bother disagreeing with you, but you're wrong, so don't assume your experience makes your opinion more valuable than other people's. It comes across as both arrogant and ignorant in equal measure. It doesn't make you sound smart, even when you are. it also doesn't make you sound right, especially when you're not.