Sorry but this post is going to be a bit messy because I'll be responding to several things and I'm tired so I don't want to use the quote button, asjkdhfkasf.
re: Swanna; keep in mind though that it gets Surf very soon after you obtain it, which is a good STAB move, as well as most of Clay's Gym to train against. It gets Fly relatively soon after. Also, I believe you get Ducklett slightly earlier than Vaporeon (though correct me if I'm wrong), so that's another plus it has. So yeah I'm sticking with it for Mid ^^;
I'll [2/3] Ninetales for Low. Sure it comes late but, like AuraWarrior said, it's not Liepard-bad.
I'm also supporting Leavanny for Low-Mid. So I guess that's [1/3] then?
I've been thinking about Weezing, and I think Mid suits it fine. Poison Gas+ Venoshock early game is a legit strategy, and I guess its physical bulk and WoW would really help in the late-game against opponents like Drayden and much of the E4. That said, I would assume it really lags behind mid-game due to its rather late evolution (Lv 35, which I would imagine would be sometime around Chargestone Cave, maybe even towards Skyla) and I think that late evolution might be enough to pull it down to Mid. I won't cast a vote for it yet, though, but just putting out my opinion.
[3/3] Druddigon for Low.
Re: some of the tierings already in the OP:
- Lucario: 'Counter' is spelt wrong in its notable moves. You can probably add Drain Punch and Shadow Ball as well.
- Azumarill: Brick Break can be added as a notable move imo
- Vaporeon: one of its cons mentions a heart scale; it gets Surf soon after Clay, though, so a heart scale isn't really that necessary.
- Sawsbuck: Double Edge as a notable move as the recoil can be healed off with Horn Leech
- Serperior: Dragon Pulse and Outrage as notable moves