High level evolutions are just a common problem with Gen V as many Pokémon evolve into their final forms in the 40s.
I also have to agree with slower, bulky Pokémon unless you have them really high level (sorta like I did when I traded my Sandstorm team from Black to Black 2 immediately after I got the eighth badge). Some of them can be good and it can depend on the game, but they just are better at individual trainer battles where their bulk keeps them alive for a while as opposed to a long series of battles where they will be worn out. In those cases, you just need to sweep through them.
The best way to go in general are fast Pokémon that hit fairly hard, have good, easy to use movepools, are found at good times, and don't have overly difficult evolution methods.
Actually, while not a Pokémon, per say, but moves with major downsides, while powerful in competitive battles, are terrible in-game. This includes most recoil moves, unless you have something with Rock Head or Magic Guard (yeah, I just found out that Magic Guard prevents that too). Close Combat is excluded since you aren't planning that the opponent will hit you at all with that move.