Looking for advice on these build ideas

Would like to try a cold damage build and work up to getting Leviathan. Thought of maybe a Nightblade with max Night Chills would be a place to start?

Would also like to try an “attack damage converted to health” build picking up the relevant devotions with that ability in them. Was again looking at Nightblade so I could dual wield weapons with the ability?

Are these builds possible, would they work well and what would be a good secondary mastery?

Sure just try any spell breaker build on the forum and use the devotions you want for it. Try Jajaja’s spellbreaker. It’s a bit outdated but still a good representation of what it can do.

Edit: Here http://www.grimdawn.com/forums/showthread.php?p=373109

He uses Whirlpool from Leviathan just like you would like to