Hello Almir, I appreciate you spending time out of your busy day to have a chat with the community. I've been reading through about 75% of these current 364 comments, and I still feel I need to throw in my two cents.
I've been Infamy V since February 13th, 2014. I was dying to be able to level up again, and get some microrewards for doing so. Even an extra 2 skill points for each tier would've been sufficient. I'm sorry but the Infamy 2.0 update turned out to be a complete letdown. I don't know what you are talking about when you say the community feedback has been mostly positive. Everyone I've talked to, and everyone on the Steam Discussions has been bashing it when all they see is MORE XP. I hope you speak the truth when you say mentioned it isn't set in stone.
In regards to the OVERKILL Pack weapon DLC... there is no reason that those weapons shouldn't benefit from ammo pick ups. The Vulcan should surely be feared... but the Buzzsaw can do what it does, with even greater performance. The RPG is essentially an AoE Thanatos. Sure it kills anything it hits instantly, but the Thanatos can do the job more efficiently. If you are worried about balance, especially considering the Vulcan doesn't need to reload... consider these revisions.
Vulcan - Will only begin to replenish ammo from pick ups, whenever the Vulcan is completely empty. You can reload at anytime with the ammo you picked up, but you will not be able to replenish ammo until it is depleted again. Ammo bags still affect it normally.
RPG - Ammo pickup with restore a percentage of incoming ammo. For example... If my RPG is completely empty/partially empty, every ammo pickup I receive will build up a percentage for a new RPG explosive. Such as 5% for each pickup. (Even 3% would be great.)
It is just something to consider. Even with these minor adjustments, I fail to see much of a balance issue. Remember, it doesn't matter how little the buff is, as long as we can still replenish ammo. I wouldn't mind picking up 20-34 ammo kits for one rocket.