I have been playing the game on and off, and only recently got to end game and got arbiter and can farm all dungeons 20. So far i havent really focused on cb team, because i was aiming  to get arbiter and gear. I have been using same champions for cb arena and dungeons, now id like to seperate my arena champions and have a specialized cb team.

I dont have the biggest champion pool, and im not trying to create the highest possible damage per key for cb possible. My main goal is to make a 3 key unm team  without using my arena champs (Arbiter, Ma Shalled, Rotos).

The team im thinking right now is.

Frozen Banshee (poison and poison sensitivity)

Gravechill Killer (poison and defence reduction)

Coffin Shmasher (attack reduction and burn)

Skullcrusher (counterattack and ally protection)

Sandlashed survivor (ally protection, buff duration and defence aura)

Mausoleum mage (debuff block, defence increase, cleanse)

Im having trouble deciding between Sandlashed Survivor and Mausoleum Mage which one should i have as 5th. Here is also picture of my other champions if you have any better ideas (not arbiter ma shalled or rotos), also u can assume i have all rares ( i dont but almost). Thanks in advance for all the help.