I found Vanillite hard to train. When I caught it, I'm all like "om nom nom ice cream" and I thought it would be fun, but nope. It's a complete ass to train, and I didn't like training it, even if it was only for one level. I then ditched that Vanillite for Sigilyph.
I found Vanillite hard to train after I caught it in the Cold Storage, and I had realized I would need a good ice type Pokemon for the last gym. When I started training it, it fainted very frequently, and I decided to just give it an Exp. Share because it wasn't worth trying to train. Once it got to the higher levels, it got more HP, and I was able to pretty much 1-hit KO the Dragon-type Pokemon in Iris' (Drayden's if you have Black) gym. Still, my Vanillish is hard to train and I still have the Exp. Share on it.
i had this same problem. I was so excited because Purrloin always seemed like a cool pokemon to me. I practically gave up on keeping it as a Pokemon by the 2nd gym, and PC'd it the moment it evolvedBefore playing Black and White, I always had interest in catching and raising a Purrloin. After finally catching one, I realized how hard it was to gain experience and level up, so I ended up giving up on training it.
This annoys me to no end. Either it faints, or you just REALLY want it to get SOME exp so you have to switch to another pokemon. And we all know how slowly pokemon gain exp when they have to split it..Any pokemon with a low defense stat is really annoying to train, because they constantly faint which means running back and forth to the pokecenter every few minutes.