Noivern is the worst one, but even then it wasn't that bad. They all got their own focused episodes aside from the catching/evolution episodes which is more than we can say for a lot of Ash's pokemon.
The problem with Noivern was that it was rarely shown training or improving as Noibat. It remained fairly novice and pretty much got it's evolution from "the power of really, really wanting it". After one unbelievable bout where he trounced both a Zapdos and TR without so much as a sweat, it's lack of training started to show.
I notice around the time of the league and Flare arc, the lack of proper development and growth from certain characters like Noivern, Goodra and Serena's team started to come into play (all of which had been pretty plot armoured and invincible up until this point). It's like at that point the writers acknowledged they hadn't really put much time into genuinely improving their skills so couldn't realistically make them look strong during the big arcs.
Tying into Noivern, I don't get why so many fans are insistent over all important Pokemon evolving in the anime and that one that doesn't hasn't been utilised fully (what BW's team doesn't get flak for in terms of rotation, it gets for so few of them evolving). Evolutions seem superficial and cheap in cases like this anyway, it was hardly the fruit of Ash and Noibat's hard work and training. I'd rather have a team of well trained pre-evolutions than go with the whole "Why haven't they evolved yet?" bandwagon, especially since most of the Pokemon tend to be more fun as characters before they evolve. I mean, we've had a first stage evolution as Ash's top-tier since the anime started, and he's produced some of the best battles.
Just evolve the ones where it can play into their actual characterisation and style in a more developed way than just 'stronger and more badass looking' (eg. Braixen and Gourgeist to become more anthropomorphic and teen-girl like to fit Serena and Jessie respectively, Goodra to fit his 'all grown up now' return to the wetlands).