There is always some kind of exploit. For example, you can kill farm at level 2, then when you get enough kills you can level up to end game.

However, there are the PvE Kills and Top Players leaderboards which are obviously only for end game players. No way to kill farm your way onto those leaderboards. Only thing that annoys me about the Top Players leaderboard is that most of the players cheated to get the wealth achievements by borrowing from friends.