Feel free to play her online but like runis said, shes banned everywhere except Australia so.....I wouldnt look into practicing with her too much, unless you just want to d-d-d-DOOM COMBO your friends into oblivion offline or grief scrubs online.
Yea, Hilde is only useful for the doom combo. If you're just looking for a new character to play around with, she's fine to learn the combo with, but if you're wanting to do competition level, you'll have a lot of flying to Australia to do to use her.