I'd put Drifloon in B tier. With Krow around, every team is packing a good flying resist, so if they predict your Acrobatics correctly then Drifloon becomes much less of a threat.
Nosepass is alright because it totally stomps a few individual threats, however most of the metagame can deal with it pretty easily. I'd go C tier.
Also since nobody has talked about it yet, I'd say Dratini for A or B tier. It finds lots of opportunities to set up, and with it's Resttalk Marvel Scale set it becomes quite bulky while being able to fire off Outrages without locking itself in. It sets up on pretty much any Pokemon whose STAB it resists, and once set up there isn't a whole lot that can stop it (and that which can is, for the most part, taken care of by SR and/or Magnemite). Altogether a solid mon.
Twas bryllyg, and ye slythy toves
Did gyre and gymble in ye wabe:
All mimsy were ye borogoves;
And ye mome raths outgrabe.