I have looked around but cannot find the clue that the new HF3 can support H.265 video codec or not. That's quite annoying!
It's always good practice to transcode highly compressed codecs like this to a more editor friendly one anyway. For windows try DNxHD. I beleive the equivalent for mac is called pro res.
Hitfilm doesn't support h.265.
NO NLE SUPPORTS h.265 yet. In fact, that comes up in the first paragraph of this review:
Tech specs for Hitfilm, including supprted video codecs are here
H.265 isn't a good choice for editing, but it would be nice to have as an export option. I'd also love to have DNxHR as an output option in HitFilm, which would be more useful in many ways, at least until HitFilm gets proper XML/AAF import/export capabilities, or is able to replace a dedicated NLE, which at least for small and medium projects is within reach IMO. I'm not so sure about doing a full feature-length film in HitFilm, but I'm optimistic.
It needs proper file interchange though; it's never going to integrate with any other workflow otherwise. I'm hoping that the Tentacle Sync tool will have an output format that will enable syncing audio + video as a batch with 100% reliability by taking advantage of timecode syncing that we can then ingest directly into HitFilm for post.