Not entirely sure about how detrimental Fahrakin's passive will be to your team, I gotta look into this later. War Mother is very good if you're only looking purely for the Atk down role, but she will definitely be replaced by champs with better utility like Sepulcher, or Jareg. Her bombs are not great for CB btw, poisons would still deal more damage. 

With that being said, I'd still pick them to replace Scyl and Kael. Not accounting for War Mother's bombs, Frozen Banshee and Fahrakin's 5% poisons should be more efficient for maximizing the debuff slots over Kael's 2.5% ones. Also you won't be needing Scyl's revive and heals with Grizzled Jarl's Def up and War Mother's consistent Atk down. Apothecary can handle the emergency heals anyway while doing his role of letting your team get more turns in. 

Finish masteries, get decent stats on your gear and I see this comp doing at least a 2 key NM. Good luck!

frozen banshee kicks kaels but on cb especially when you have ally attack champ or counter attack champ 

post up your champs via screen shots see if we can see anything to help you out