I can already see a couple of good teams for specific content. Some that come to mind are:
- Spider - Sicia (HP Burn), Miscreated Monster (shield), Achak (Freeze) and Coldheart (damage). You have a fifth slot for flexibility
- Dragon - As drone mentioned, when built properly Tomb Lord can actually solo this dungeon himself, which means you can level some food up while collecting artifacts. Still, until you get to that stage you can take in a few other champs too, such as Stag Knight, Kael, Scyl, Ninja, Apoc or Vogoth.
- Arena - A generally easy arena team to aim for is one that boosts turn meter, drops enemy defense, increase your damage (through either increase attack or increase defense, depending on your nuker), and then nuke. Champions like High Khatun (turn meter) and Madam Serris (reduce defense and attack) help here. Infact Madam Serris is one of the best because she also removes other buffs, including shields. Kael and Ninja can nuke, as can Aleksandr.
Dark Elhain can be another nuking option as she also gives herself her own increase attack, which means you can actually bring in 2 nukers (High Khatun to Madam Serris to Dark Elhain to Ninja, with the last champ freezing any survivors)
Doom Tower - Vogoth, Stag Knight, Tomb Lord, Apoc and Miscreated Monster are good options. Ideally you want reduced attack and defense on a lot, as well as good crowd control. HP Burn and Poison helps a lot with damage in the later levels.
I'm not suggesting that you build out all of the above champions straight away, but wanted to show that different champs can help different scenarios in late game, so it won't just be a single roster of 5 doing all the hard work. You will want to focus specifically on an area that is giving you some challenge, and then the champions that will help in that area.
Also, you have a lot of level 50's there at the moment. I wouldn't spread yourself too thin just yet. Focus on getting some more to level 60
Finally, I didn't go too much into Clan Boss but this is another important area that you need to build a team specifically for. Speed tuning Clan Boss is one of the more critical parts of the game, and depending on the speeds the champs used there might not be used much elsewhere in the game. Who do you use at the moment for CB?