Of course it’s too strong, and we’ll see more and more of it monstrously boosted until the next balancing update in a few months, or until nerfed. There is no reason for Monolometrodon to have these stats and these resistances, apart from Ludia’s glaring inability to balance their game. I’ve been leveling up mine to replace Magna since the damn Irritator is barely spawning (1-2 per hours of waiting at night is nothing).
Note that I don’t mind Mono being strong - sure, why not. What annoys me is the existence of a higher tier similar creature, much harder to make and level up, offering barely any improvement over this legendary. It’s just one of the quite many instances where balancing is a complete failure.