A good balanced system would be to put three or four Deathclaws (insert Skyrim equivalent here) in a certain region that are a much higher level, but being as there are only three or four you can evade them and it doesn't make the territory completely untouchable.
Think about how long it takes you to level. Would a few 'Skyrim deathclaw equivalent's keep you entertained for long? No. You be level 50-60, and you'd go fight them for an hour then they would be dead and you'd still be out of content. You want content for another 30 levels (to 81). That's 60% (30/50) more content. They simply didn't add that much.