I really don't get what Scarf Koffing's going to be revenging, so I'd drop it. Also STAB Poison sucks.
Tank, on the other hand, is pretty good. Fatty used something like this iirc
Koffing @ Eviolite
Eviolite
Bold 196/0/236/0/76/0
- Clear Smog
- Will-O-Wisp
- Rest
- Sleep Talk
Shuts down a lot of physical sweepers pretty well (bar Meditite / Gligar, who it needs to wisp on the switch to have any chance of taking on, and Taunt Gligar still shuts it down pretty well). 23/30/18 defenses are pretty damn impressive, and it has excellent typing for an LC physical tank. Can't do much to special sweepers but it shuts down Sraggy pretty nicely, even outstalling it unless it gets absurdly lucky with Shed Skin recovery.