Your team has no decrease atk champ, that's why you are doing such a small ammount of damage. Probably the fight is over quite early. In addition to that, you have no way to fill the lifebar of your champs (exept the two wearing life steal). 

Lodric and Grush (for leech debuff) should join. Also make sure that every champ you use at CB has Warmaster or Giantslayer masterie, otherwise they don't heal enough from leech.

Thanks a lot Skadi, will try with leech champs for next key! 

Yes, the most of the existing champs have Warmaster, but in order to redo some of them I need to be certain that they fit into a CB team composition. Which I'm not atm

You do have Drokgul - Deadwoodjedi has a build for a Maneater-Drokgul unkillable here: https://www.deadwoodjedi.com/speed-tunes-4/Drokgul-Unkillable 

Bit trickier than a classic Maneater-PK one perhaps, but it should still work and get you probably a 3-key UNM team. 

Alternatively, you could just speed tune a counterattack team with Skullcrusher, no unkillable, but then you really need to invest in defense - decrease attack on CB and increase def on your own team, maybe leech, ally protect,... 

Lose Gravechill for sure, Lyss would probably complicate speed tuning and might best be replaced as well. 

In most cases Warmaster/Giantslayer is the best tier 6 mastery anyway, for dungeons and faction war bosses. Of course this is a rule of thumb, not a rule. Arena nukers should use Helmsmasher, Arena debuffers maybe Eagle Eye, for Revivers you could think about Timely Interrvention. But everybody who has not a special job that is supported by a certain tier 6 mastery should have Warmaster or Giantslayer, that's the standard tier 6 mastery.

I would build the UNK team listed- its the easiest way to start getting top chests.

Of course. I just need to understand the roles in an UNK team and search needed abilities amoung my existning champs :)

Click the link provided above, you have the champs.  

Truthfully,  you  don't have  to  change anything.

Your  current  team  can  unlock  the  100  Mil  NM  CB  Damage  mission.

You  said  your  team  does  10-13  Mil  NM  CB  Damage.

Lets  say  your  team  does  the  minimum amount  10  Mil

To  unlock  the  mission,  you  would  need  to  do  10  CB  Keys  in  a  24  hour  time  period.

10  Mil  times  10  CB  key  fights  =  100  Mil  CB  Damage.

1  CB  Key  =  100  Gems

10  CB  Keys  =  1k  Gems

Obviously,  improving  your  CB  team  can  help  reduce  the  gem  cost,  I  just  wanted  you  to  know  that  you  can  do  it  with  your  current team.

Sometimes, people don't  know  about  how  missions are  unlocked.

Thanks a lot for your tips, I managed to increase NM to 20-25M with this team on void (more when force CB), thought gear is not trimmed to perfection so there is room for more!

i