Well, there's a possibility that Volc will get Mega Drain seeing as its a TM in Gen 1 and it learns Giga Drain, so that might be an option. Rest is probably the better option though even if it gets Mega Drain though because of healing and status removal (primarily paralysis).I think I got confused with Mega Drain then. Well it got a lot worse now, so it's probably not as OP as I expected, still really good though, even when I have no idea what to run as a fourth move on. Luckily it can be checked decently by rock and water types now, as long as they can survive a +2 Psychic/Fire Blast. Rest is probably the best so it can keep its HP up.