What is an appropriate nerf for an Epic Ardent using Demoralizing Strike?

Question

Demoralizing Strike is a 1st level Ardent at-will. Of interest here is the Augment 2 (sample build):

Augment 2

Close: burst 1

Target: Each creature in burst

Hit: 1[W] + Charisma modifier damage, and the target takes a penalty to all defenses equal to 1 + your Constitution modifier until the end of your next turn.

By epic level, all things being equal, this turns into a -6 to -8 defenses debuff until end of next turn that can be repeated 6 times during the encounter, turning all monsters around the ardent into things that can be automatically hit.

What is the best way to determine what the debuff should be, such that the ardent can have a meaningful effect on battles (more than -2, which is just token) without trivializing them?

Answer 1

Righteous Brand, the Cleric at will was changed from granting a +Strength modifier to hit to an ally's attack on your target, to giving a flat +3 to hit for very similar reasons.

A flat -3 or -4 to defenses would be potent even for a psuedo-daily, and at low levels is probably unchanged in power.

Another alternative would be to make it cost more power points to drop defenses further. 2PP -3, spend additional power points for additional -1's

Additionally, you could change it so that it only debuffs the defense of the Ardent's choice, or change it so that the debuff expires at the beginning of the Ardent's turn (meaning that the follow-up demoralization is against normal defenses rather than demoralized defenses).

Tactically, as a DM, use ranged monsters and skirmishers that can keep themselves away from the Ardent.

Answer 2

Is it that unbalanced? There are several powers have similar effects, though they target One Creature instead of Close Burst 1.

Great Dragon War Cry is a Warlord Attack 23:

Target: One Creature
Hit: 3[W] + Strength modifier damage, and the target is weakened until the end of your next
Inspiring Presence: Until the end of the encounter, your allies gain a power bonus to their attack rolls against weakened enemies equal to your Charisma modifier.

Great Dragon War Cry effectively gives the creature an equivalent debuff. It is an Encounter power, but it stays in effect until the end of the encounter and it weakens the target for a round.

Similarly the Psion 1st level at-will Mind Thrust:

Target: One Creature
Augment 2:
2dl0 + Intelligence modifier psychic damage, and the target takes a penalty to all defenses equal to your Charisma modifier until the end of your next turn.