Where are you having problems? The waves or the boss himself?

For the boss there are some key components. For example turnmeter control, counterattack and reflect damage and multihits

Counter attack and reflect damage should preferably be on all allies.

For the most part youll need atleast one of these. My team is set up with Martyr for the counterattacks - Coldheart for the turnmeter control and damage - Zavia for the poisons and multihits, Apothecary for the multihits and speed boost, Reliquary Tender for the revive since my Coldheart tends to go down during waves.

You could technically just use multihits and alot of turnmeter manipulation. The idea with that is that you take the shield down and then he never gets a turn. I think this is the main strategy used by most ppl in the endgame.

Fellhound and Apothecary are 2 great budget options for FK. There are more but these are the 2 that I can think of in a rush.

OPs roster from an older thread. 

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Can't say for sure if they're missing any champs, or updates to the roster.

So something like Lys/Rhazin/Visix/Scyl/Armiger? There's a few routes to go if the gearing is OK.