[@Unlucky0013]

Your opponent's level x10. So a level 1 would yield 10 ep; not really worth it. Level 9 would yield 90 exp, which is almost Boss level. However if you kill an Outlaw, you add 5 to that 10, so a level 9 Outlaw would drop x15: 135 EXP. If you're a at most level 6 and take out a level 9 Outlaw, that bumps up the multiplayer to x18, making it 162, better then most at-level bosses. Good luck trying to find someone willing to die as an outlaw though, cause if they do they lose a level automatically. 

And for the curios, yes you could tackle a boss three levels higher then you for 300 exp, since 100 is the average and the EXP multiplier caps at 3.