Cruel Cut Style

Prerequisite: Wis 13, any martial class
Benefit: You gain a benefit with any of the following powers you possess.
Cleave (fighter): If no other enemies are adjacent to the target when you hit the target with this exploit, the target takes ongoing damage equal to your Wisdom modifier (save ends).
Furious Smash (warlord): If your ally hits with the attack this exploit provides, the target takes ongoing damage equal to your Wisdom modifier (save ends).
Predator’s Strike (ranger): If your beast companion hits with this exploit against a creature granting combat advantage to it, instead of adding your Wisdom modifier to the damage roll, you can have the target take ongoing damage equal to your Wisdom modifier (save ends).
Riposte Strike (rogue): If you hit with the riposte this exploit grants, the target takes ongoing damage equal to your Wisdom modifier (save ends).

Might try this for at-will's to get ongoing.

On a side note, I used to play a rogue that was focused on doing high levels of ongoing damage with penalties vs the saves. It was alot of fun, but tough to do very often, since ongoing damage, at least for rogues, tends to come exclusively from daily powers and items.