I got this one from ogaming.
I found it quite crafty, and thought I'd share.
1. Work on a Lore & Legend quest (any you feel like) until you are one study item away from completing it.
2. Acquire the item (get the drop or just buy it) that you need to finish the quest but do NOT examine it for the quest update/completion.
3. Exp to 99%
4. Enter the arena and turn OFF combat experience.
5. Examine the L&L item but do NOT hit the "Study this item" button in the dialogue box that pops up.
6. Move the dialogue box so that it is out of your way, but leave it open.
7. Fight your way to the Pit Champion. During the "rest" period between fights before you have the champion come out, turn experience BACK ON.
8. Begin the fight with the Champion. When you are low on health and power and it looks like he is going to win, click the Study Item option in the dialogue box. This will complete the L&L quest, give you experience that will cause you to ding to the next level (You did do step 3, right?) putting you a level over what the Champ was spawned for, and most importantly you will get the full health & power refill that comes with gaining a level.
9. Kill the Champion.
10. Collect underpants.
11. ...
12. Profit.
This strategy will work at any 10% milemark for any level. If you complete the L&L quest as described above the exp will put you over 10, 20, 30, 40, whatever % you were about to go over, giving you the free complete heal and power refill. I just suggest doing it at 99% as opposed to 49, 59, or what have you because well...you level and get stronger in addition to the health refill...and really...too much overkill is never a bad thing.
I found it quite crafty, and thought I'd share.