I played BW when it was first released and saved the post game for the english version to save some of it. So, my memory may be hazy but here is what I used for my playthrough:
Samurott: He never really hit hard and took a lot of damage too late game but all in all, he's a pretty good all rounder. He helped me a lot in the gyms+E4 and was relatively easy to train with the Lucky egg. To be honest though, the other pokemon in the team just outperformed him. That may be because he was Naive and probably had shit IVs. Despite that, he belongs in Mid High Tier.
Doryuuzu: The star player in the team. Seriously, you get him early, he evolves pretty quick, is easy to train and hits hard. Best of all, he can take hits due to his...steelness...Anyways,This guy owned the Elite four. Top Tier for sure.
Denchura: Another good player. If I remember correctly, you get him around level 28-29. I got mine at 27 with compoundeyes and timid(of course after releasing the bad ones). He hits stuff hard with a pretty damn accurate Thunder. This guy was awesome and easy to train. Even in the Elite four, he would mostly 1-2HKO the foes. High Tier.
Cofragrigus: I used him because I thought I needed more defense because all my pokemon were very fragile. But he just doesn't hit hard and never really became useful so I replaced him with:
Chandelure: Not gonna lie. He was damn hard to train. When he was litwick and even Lampent, he would die with the slightest touch. And things hits pretty harder than slight mid to late game. But when he evolved, man did he hit hard. He still died pretty easily though but that's only when he failed to inflict massive pain and OHKO the enemy, which he did most of the time. Was it worth it? Probably. Would I pick him again? Not really. Too much pain to go through to get him to be amazing. Mid low tier.
Beartic: I got him for the 8th gym because none of my other pokemon could really go against dragons but man he is such a pain. It was easy to evolve him and stuff but he doesn't really get any good attacks. All he gets is icicle drops and that's just not good enough. I held on to him until after the gym and then deposited him in the box. Low tier.
And then I used A pidove evolution for my flier.
But I was way too weak for the E4. There was no way I could've beaten them with four-ish pokemon (I guess Beartic could have been useful but I didn't want to use him. He was a pain :().
So I caught a Monozu and spent a whole day to train him:
Sazandora: What can I say? I couldn't have won the elite four without him. I know he can be a pain to train but he was really worth it. Oh and I had to do the training without the Lucky Egg btw. I lost my lucky egg when i accidently released my cofragigus instead of taking the lucky egg from him and I couldn't restart because I caught a good candle by that time and I forgot to save -__-.
Anyways, even when he was a Jiheddo, he held his own. I had to baby him for a bit but when he evolved, everyone was decimated by his power. :) Mid Tier