Most of Molten's stuff like his roar weapon, rock throw and spin aren't a problem, but his lingering blast clouds can be a pain and he's wide enough that it's not always easy to roll away from his enraged charges. He does tire out really fast though which makes it easy to get in lots of head shots. The problem is I was hitting him so hard he'd be capturable before I'd get in the head break sometimes, but I just wanted to get the hunts over with fast.
I might try farming
this quest for the lone mantle I need before trying it online. If I break heads and capture both for the fangs, the odds of a mantle aren't half bad. It'll be good practice at the very least.