I would build up Fellhound and Soulbond for FK as well. Would not use UDK there, he will be great for Dragon and Ice Golem and Spider.
Soulbond can also help on spider.
Apothecary can help a lot in many cases.
Frozen Banshee can help on Dragon (and CB) as well. I do see the makings of a decent CB team with Fayne, Frozen Banshee, Geomancer, UDK, Anax, Renegade etc. I would focus on CB next, because the resources you will get there will help you more. Lots of ways to go there.
Scarab king is tough and you will probably need a team of 60s and 50s to beat him. From what you have Armiger, High Khatun, Soulbond will help and probably need 2 more AoE shield champions on shield sets. Metalshaper, Draconis, Scrapper are all rares who can do this. But all of them have to be build.
That said, you next priorities should probably be getting Geomancer and UDK to 60. I would not put any more resources on Warpriest and start replacing her with Apothecary in non FW content.
Good luck!