You put your finger right on the issue

There's literally no way to keep a nice depth (cause let's be honest you only have 2 3rd line caliber players here, AA and Mikeyev) if the big four stays together. Tho a solution might be to move Holl and to get cap room there

I don't think they have to make too many more moves to make cap space. Could just run with a 20/21 man roster (obviously not ideal) and have emergency call ups if needed.

I think it would be a mistake to move Dermott right now, he isn't going to cost that much with his new contract and he is still developing. Jumbo Joe would cost less than AA, which would allow them to keep a little more cap space.

Its not depth vs Core four but depth vs Finaly Decent D

Premium Contracts ( aka overpay ) and flat Cap on top prevented TML to have both. Core Four are big distraction but they should stay as they are

Holl and Kerfoot ditched could allow another 3-4M Defenceman to be landed but Dubarelli missed the chance to overhaul 3rd Line with quality ( i hoped he would dig into Janmark, Fast, Wallmark, Larsson or even Wennberg for 6M 3rd Line instead 10M that TML had last year, cause our kids are usualy scammed into cheap 2M contracts )