DTube is open source and saves your key only locally on your computer. Hopefully they will integrate SteemConnect sooner than later. But even if your private posting key would get compromised it would only give access to posting, commenting and curating. No transactions. And you could then reset all keys. I never needed to do that so far.
Please keep in mind that DTube does take a beneficiary reward fee from your post. Last time I checked it was something between 15-25%. Check out latest post.
RE: Steemy EP. 43: How to Upload a Video on DTube