Since there's a special event going on in Dauntless this week, I've been grinding a lot of umbral escalations over the weekend, so I've been toying with a new build to get through solo escalation as fast as possible, and this is the build I've come up with.

https://www.dauntless-builder.com/b/YjUxYf8CJBTRwUzc4fmTKTkJFdTJPcLC7KI0btBCeEc0acAC3zirURCmWIeCRZ

Essentially:
Berserker, Predator, Rage, Wild Frenzy and Discipline are all just to create a stupid amount of Attack power.
Energized and Evasion is there to make sure that you can continually spam: Special (repeaters dance) followed by two light attacks during the invulnerability frames.
The Conditioning is simply there because I couldn't find a way to build in anything more useful. And an added benefit, you'll basically have fully regenerated your stamina after a single attack cycle (special, attack, attack).