Trolls, Giants, Mamoths, and any enemy with a similar looking HP bar should kick my ass until I am leveled enough. This method used to be a decent and accepted way of how games worked and has been lost in time because everyone is a Mary Sue and you're encouraging this behavior. Everyone wants to be god. Working yourself up to a goal should not be put aside and must be encouraged even more. If you don't want to fight a non-common enemy because you can't beat it, avoid it, they are not common.