I think 6 stamina regen is the number I've heard quoted most often and what worked for me during the beta. All things are, of course, subject to change. Also, for a number of reasons, I wouldn't rush into making the conversion of a human or elf character to a gargoyle until you know what gear you will also be able to convert or to craft from scratch, including earring and necklace pieces.
I believe Chrissay said something a week or so ago to confirm that after the expansion is released, there will be a test shard where people can try out the new content, as long as they have already purchased and applied an expansion code to their account. I would certainly recommend taking advantage of that test shard once it's up if you are considering making a new gargoyle character or converting a human or elf character to a gargoyle one so you know what to expect.