Just completed the campaign, did it on Hardened for the Gold trophy. 95% of the campaign was a chore, I was just waiting for the thing to end. Plus, the amount of times you will almost certainly die first time is ridiculous, some bits are 'wtf' and take mutliple tries and it can get very frustrating. Meh.
Edit to save the triple post
thanks for Jay/Oxy/S-C/arbitrary member
for hyping the Tar. Added the old silencer, obviously, and found that it's amazing without stopping power today. I just think it's a quality gun, kinda like the ACR but more badass and the fire rate is incredible. The only downside is the ammo consumption, so therefore I put on scavenger. By creating this deathchild I came up with this class that is wholesomely made of win:
Tar - Silenced
Thumper (I went there)
Semtex & Smk Grenade (whatever sec.grenade you prefer)
Scavenger, Cold-Blooded, Commando Pro.
It is triumph-ful. You could replace the ol' thumper with a foregrip SPAS but whatever, the scavenger makes this amazingly fun, being able to tube and nade at will, you get so many kills from them, just great for clearing stuff out and testing areas/getting random or hopeful kills.
Also, use the UAV. I don't care if it seems like a waste of a streak, it's fun having it there, and getting standard kills is more fun than air support +100s.