I'm of the view that they're nice to have, but surviving > everything.
I mean I'm not quite capped for either, but I have no threat issues at all so I've dumped all my gemming and gearing in to survival.
I think it all depends on what you need and what you're struggling with. If you're struggling with threat then hit and exp are going to help enormously. If you're fine for threat then the best thing you can do is up your survivability IMO