Agreed...Air NZ do NOT intentionally avoid Wellington with the A320...as stated, there are at least 2 of them there every night ex the Tasman routes.
Having flown the A320 into Wellington on quite a few occasions, I can tell you it is not a big deal....would I feel as comfortable on a crappy day as in a 737? Maybe not, but that's just because I've not been there as many times in the Airbus. Most Air NZ pilots will tell you the same thing.
I do agree that leaping into WLG and Queenstown with inexperienced crews is not a good idea, but you only get experience through exposure. Any Captain (or F/O) with a bit of experience and a lot of common sense will have no problems with either place....you don't need to be superman!
BTW I think I've flown into WLG over 10 000 times in my career....only had big concerns a handful of times.