It’s not hard at all if you can make a 1 on 1 tackle.I would say it's the hardest position to defend but not the most important.
If your team is controlling the ruck well, the ball rarely makes it out to the edge. Melbourne do this very well.
The hardest position is the halves as you depend on the inside pressure taking away time from a backline movement your centre being aware he isn’t overlapped and your winger holding ground and not making a 45 degree rush in field.