You're fortunate - Riho Bonespear is amazing. You have most of the pieces of a good team. Something like:

Riho Bonespear (DEF down, Weaken, ATK down, CR down)

Frozen Banshee (Poison, Poison Sensitivity - turn off A2)

Mausoleum Mage (DEF up, Cleanse Stun)

Vogoth (Leech, debuff extend - turn off A2) 

What you're missing is a good counterattack champ. I don't see any in your list unfortunately. Without that, you're going to be missing out on a lot of damage. Your best bet may be to fill that last spot with another poisoner while waiting. Toragi the Frog is alright, but really you'll probably just want another Frozen Banshee.

Much appreciated...

And you are right, among many good champs, I do not have a single counterattack or unkillable option :)

The problem with Riho is that it takes too many books and unlucky me put all my remaining 7 books on her and end up maximizing the A3, and no lvl ups in A2, which is the main ability for CB... 

I am already building my Frozen Banshee (recently summoned). So based on this suggestion I may consider Mausoleum Mage and Vogoth for the queue.

Thanks a lot...

You can still get over 25 million a key without counterattack - i get 35 million a key (annoyingly just short of one key) on nm without a counter attack

kramaswamies suggestions sound good... it might be a gear issue??  

As for two poisoners, when i ran two poisoners i had problems on auto because the debuff bar would fill and if attack down had failed there would be no space to reapply it.

Might be worth trying but something to bear in mind..

Got it... Yeah double poison and auto run issue is in my mind. I am down to run manual as long as I do 2 key runs.

Gearwise I am not the greatest but not bad as well. My team can hit 190+ speed on all of them and 180+ accuracy for whoever needs it. If there is a gear problem, it may be that I do not use lifesteal gear of all my champs... Only Frozen Banshee is on lifesteal...

So I will try this team, but Riho will be a problem as her A2 is not leveled. If I can get an alternative to her...

The problem with not using Riho is you basically need two other champs to fill her spot. She is the only champ in the game IIRC that has Weaken, DEF down, AND ATK down. Most champs have the former or the latter, not both.

If you can't use her, Rhazin is probably your next best bet, and then for the ATK down, someone like Tayrel.

Riho actually has cleanse too :)

So I will try Riho, Vogoth, Frozen Banshee, (Ursala or Coffin Smasher or Tayrel for extra decrease attack as Riho's cool down is long on that one), and finally someone to increase speed may be?

Hope this makes sense at all... 

Mausoleum mage is useful because of the DEF up as well. If you aren't going to use him, you'll have to find someone else with that ability, as it's 100% essential. Increase speed is not actually useful on CB, throws off your rotations.

Instead of wasting resources for non-decent champs, I would wait till having good champs for clan boss. Simply tap on champ's reviews, thousands players would not vote wrong. 

Thank you all for the suggestions.

Something amazing happened today. As soon as I got my Frozen Banshee fully built-up, I got my first ever 20M damage with following team:

Tayrel, Apothecary, Scyl of Drakes, Frozen Banshee, Kael

i

For the moment I have fufilled my 2 key goal. Now I can look further to replace Scyl and Kael with other options...

Cheers.

Fantastic, gratz :) 

Being able to 2 key NM for the first time is a nice feeling!

Pain Keeper could help with your Riho problem.  or another cooldown lower/reset champ

For the first time I made an in-game purchase for 5 pcs of epic  skill books.  together with the ones that I was colleccting,  my Riho is fully booked now...

And I have a solid 2 key NM CB team :) In fact around 23 mio damager per key...

Thanks everyone.

gratz well done - its definately a nice feeling hitting top chest regularly - hope the rng gods drop plenty of void and sacred shards for you