Is there a resource for figuring out enemy (specifically Boss) HP? or is it something you need to figure out for yourself?

The official guide by Prima Games lists things like total HP and pretty much anything else there is to know about a given enemy, and is what I've used for help with routing. Although, if I'm not mistaken, I think you can check the in-game monster compendium entries for the HP total and other information on an enemy, but I could be remembering wrong.

I Checked the compendium before I asked, sadly it doesn't give HP totals but thank you. I'll have to look into getting a game guide.