I think im fine with it as long as there are options, including running away. In some games, like PF2, you wouldn't be able to. (Though, PF2 is pretty clear not to send manticores at level 1 characters.)The manticore example struck me, since what was seemingly annoying about it is that it is an unbalanced encounter for level 1 characters. Unbalanced there means that it is overly deadly if engaged in straight combat. I personally don't see the problem with that; that's when you come up with other strategies (including running away).