So here's my proposed replacement:
Mighty Roar (Lion Racial Power)
Encounter, Minor Action, Aura 5, Sonic, Fear
Targets: All non-allied creatures in area of size large or smaller
Attack: Cha + 2 vs. Will
Hit: Target is dazed and takes a -2 penalty to attack rolls until the beginning of your next turn.
Miss: Target takes a -2 penalty to attack rolls until the beginning of your next turn.
Critical (Natural 20): You may take a healing surge as a free action.
Improvement: The attack becomes Cha + 4 at 11th level and lasts a number of turns up to the lion's Cha modifier (save ends; minimum 1).
My thinking: the idea behind the mighty roar is to create a fear-like effect that doesn't just send the foes running off to attack somebody else (since lions are natural-born tanks and probably want to keep the baddies' attention on themselves). Thus, the targets are dazed (frozen in their tracks, so to speak, and only able to take a single action) or simply rattled (with the -2 to attack rolls). The healing surge on a critical is pretty straightforward — cutting loose with a nice deep roar can just get the lion's blood racing again! I was trying to come up with something on par with the dragonborn's breath weapon, which is basically a free burning hands (or acid hands, freezing hands, whatever) once per encounter.
Thoughts? Ideas? Rotten fruit?