Hello tattboi26 and welcome to Cruise-Chat,
the best answer I can give is, "could be!' I did the same trip (in reverse order) in 2002 and it was smooth all the way from Auckland to Sydney. But I've heard others say it can be pretty rough.
However of more concern than Bass Strait would be the Tasman Sea itself; rather notorious for high seas. I crossed in February with no problem, but there was a guest lecturer aboard who had photos of an earlier crossing that were pretty unsettling--waves crashing over the bow--I was surprised Princess let him show those photos; kind of like having "United 93" for the in-flight movie.
Anyway, my advice would be to pay attention to the ship announcements concerning weather and seas; they are good about giving you advance warning. Use a patch or dramamine and don't wait until it gets bad--then it's too late. Most important, don't worry about it and have a great trip. It was one of my best ever.