This exploit was used by me for quite a while. It requires a level 20-23 character to assist a level 17-20 character in zoning into an epic zone. Epic zones give a MASSIVE experience bonus over heroic zones. For example, Von3 on epic was giving me 150k exp for a first run, whereas the best exp zone for 17-20, monistary of the scorpion, only gives 30-40k.
Here is how it works.
1) Have a level 20-23 character group with a 17-19 character
2) Make the level 20 character the leader of the group.
3) Have the level 20 zone into the heroic instance.
4) The level 20 then must zone out of the heroic instance.
5) IMPORTANT STEP: Have the 17-19 character(s) 'grab the window' ... most people in DDO knows what this means
6) Reset the zone with the level 20 character
7) Have the level 20 zone into the epic version of the zone

Now the level 17 is in an epic zone getting full exp
**Notes for the less experienced in DDO
*I use a level 20-23 character to avoid power level penalties, 20 -> 17 gives no penalty... 21,18... 22,19
*This can only be done in a zone with a heroic and epic version of the zone (Von, LoD, druids deep, deasert zones... there are a ton.
Rather than 20 hours minimum (Very fast legitly), I level a 17 character to 20 in 4 hours.