I'd rather we keep the gauge cost of Onslaught. I wouldn't want to mindlessly be able to just dash towards a target, I want some thought in it;
"Do I sacrifice 20 BG to quickly keep up with my GCDs and overall rotation, or do I sacrifice my active DPS to get an instant chunk of damage in by Fell Cleave after 3 seconds of running?"

Besides, it'd just turn into another button you spam for DPS if the damage ain't removed. That I do not want.

I want it to instead serve as mobility with a bonus attached to it.