Increasing the dungeon stages has absolutely low proirity for now. An unascended lvl 40 Armiger doesn't help.

The only way to get forward for you now is campaign 12.3 brutal, minotaur and potion keeps to get the full power of your champs. The strenght of champs in Raid does not increase linear. The difference between lvl 50 and lvl 60 is not 5/6 to 6/6. A lvl 60 champ is twice as strong as his own lvl 50 version. Your champs are just not able to beat higher dungeon stages right now. With lvl 40, they are to weak.

I would lvl up Ronda and Armiger next. But not only bringing them to lvl 60, also get full ascension (potion keeps) and full masteries from Minotaur.

/edit: I would change my recommendation for the next lvl 60 champ to Daithi, Ronda, Armiger.

Thanks for the suggestions and guidance.  I was heavily leaning towards Daithi as my next 60.  My only concern was whether I should 60 Sepulcher Sentinel first for Clan Boss.  Given Daithi is on my arena team which is in Gold but just barely treading water, I did want to level him first.  I'll actually be able to do that tomorrow.  Ronda will take a while.
Similarly, I've been waiting until CvC to ascend my champs.  Had I waited 2 days to post, you would have seen a lot more ascensions on the champs you indicated though I don't know if I have enough potions to max them all.  That will be my next priority.

I think Daithis masteries are maxed out (I'd have to check) and I've already started training up Ronda.  I hadn't started working on Armiger yet as I just very recently started trying to use him for this.  Actually, assuming Daithi is maxed on masteries and as I'm pulling Crohnam tomorrow for my Spider team (stuck at lvl 10), it looks like Crohnam, Ronda and Armiger will be the next 3 I work on masteries.  I need UDK and Elhain to farm 100% Mino 15, so that works out perfectly.

Thanks again for the help.  Much appreciated.