Yeah, if it affected friendlies, you'd see abuse with fire eater pretty much immediately (as in, even I would jump on board that train).
I though the same, but let's think a way to doesn't make it kinda stupid. I mean with this you can just zone enemy champs without drawback. And the new hyaenid with this ability, it's like "yo, free 12 dmg"
While occupying the terrain. Enter the terrain, gain inhibited before the 12 damage; leave it, lose inhibited
Personally i think Trail: Fire Wall should be an activated ability. This dashing hyena is the only champ i've seen that can make constant use out of the ability. Everyone else requires too much set up and is situational. I've never really cared for Firewall beyond the font assault. This new champ actually makes me want to use him. Now if it was activated and i could stealth my Trail unit and then position him behind an enemy champ(s) to make a wall then use a knockback mech, id find the ability far more useful.