Phoenix v assault battles

Has anyone had any success with phoenix v ground war or Imperial might mythic to challenge tiers?

I'm already gearing cls, Han, Chewie, r2 and C3PO for Imperial might; but they are queued up behind the need to boost some ds squads.
I also need better fleet. I'm running gr under mace, but it's not working even with r7 jka and ahsoka + g12+ 5s, ht, Sgt, etc. Losing to decent rebel meta, timing out against 6* negotiators...and let's not even mention malevolence.

I know phoenix aren't great, but I need to get into those challenge tiers for gear/relic mats, etc. And the fleet boost would help.
I could farm NS, but I'm trying to focus on gearing what I have over farming; and I'm missing talzin, zombie, spirit...and only ventress is beyond about g5.

I'm also looking at running Ezra (+Kanan??) under luke when I get him.

So potential efficiency in gearing if I gear phoenix and use the rewards from those events to fund other better toons.....or will phoenix simply fail to pass the tiers?
My current phoenix has zeta on Ezra and sabine, who are g10. Others g8 approx.