There aren't any WMD's, not to be rude, but you just need to get better. SMAW? E. Focus+imp. armor, Phase Rifle, double armor or E. Focus carby. Phase Rifle? double armor. Reverse Damage? Get a OHK weapon or run away.
Really, almost everything can be beaten with a Carby tank and E. Focus+movement upgrades+imp. armor/melee SPAS with an HVS secondary for long range.
No offense taken. I do need to get better. I never pretended to be the most awesomest con2 player evar. But its kinda hard to work on that with the Smaw. Theres no getting better against smaws or in this case, the taco shooter. I could choose those perks you mentioned, but i'd have to take away perks from my weapons So i have to choose between surviving and damage.
You should try experimenting with different weapons and perks. Then once you find four well balanced loadouts, you shouldn't have a problem countering these weapons.