I like the concept of the mythic. It can perform well ST with Den. Don't see it being an issue in PVP due to it's limitations (also real burst with it). However some ideas to make it competitive in end game PVE.

- The game needs things that can compete with the DPS of Arcs. So to summarize Arc DPS strengths. It's pretty bursty. It has amazing AOE. It's not that reliant on ground dots (good for mobile fights). It has the unique ability to deal damage in a straight line 20m in front of you & 5m behind you are the same time. It's also pretty easy to pull off. For these reason's it's been king in PVE DPS since it's been released. Along with other reasons (Sustain is very good & Survivability is good with prag.
- The new mythic on Den can hit 180k ST. Which is greater than Beam Arc's ST. However the AOE is very low. It's pretty reliant on ground dots & the sustain is atrocious. In content these DPS wouldn't be able to wear ult proc sets (like Warmachine). For these reasons, you won't see this mythic get much use in PVE end game.

I'd like to see the mythic lower its damage modifier for status effects. Which would reduce it's ST ceiling. However introduce another effect that would increase it's AOE output & read something like this:

"(1 item) Increase your damage done with status effects by 1% for every 1 Ultimate you have, up to X% (adjusted to balance, maybe dropped to 130ish?). Both the current and maximum damage done is halved against Players. While you have 170 or more Ultimate, your status effects burst in an 10m area applying the status effect to all other targets. This can happen up to once per sec. Applies Minor Timidity to you, consuming 1 Ultimate every 1.5 seconds while in combat."

Adjust the values so for stationary targets Den's might actually do more AOE damage than Arc. However for mobile fights. Or fights where enemies are spaced more than 10m's apart. Arc still retains an edge in those encounters.