I don't have nagaraja or wadatsumi, but I did get Kirin the other day. I don't have her leveled up or maxed yet. She's probably a bit better than the other light 5* you can get from events, but not at the same level as the human gacha senki. I'd expect the same for Nagaraja- better than Yaksha/Ibariki Douji/Yamata no Orici, but not better than human fire senki. Looking at a guild mates copy, I'd say that's the case.