I went ahead and bought Killer Prime, and he makes so much difference? Went from barely being able to beat Insanity on manual,to a 3-4min auto. Only had one loss so far. Might actually be able to get the awakening materials and the T1 cosmic now!
This is mid-range-ish team. It's not great, and uses a few event-exclusive talismans/characters, but should be a decent starting point to help people with their own team building. Have included my reasoning. As long as you can deal with Perfect Immunity and Perfect Immortality, you should be ok.
Flight of Icarus Eddie Lantern, Warlord, Cosmic My strongest Eddie, capable of dealing huge amounts of multi-hit damage when Warlord triggers. Can cleanse and remove damage shields The Killer Prime Persecution, Shell, Cosmic His permadeath passive helps deal with the Light talismans, and Bloodlust from his basic helps trigger my Warlords. He hits like a wet noodle beacuse I don't have any good talismans for him yet, but his job is to stay alive and debuff the enemy. 6* Warrior LoL Orbits Awakening his first level turns his basic attack into an AOE that removes Perfect Immunity, which a lot of enemies in here have. The Orbits help him cleanse your team and purge the enemy's buffs. The Orbits also mean the final Cyborg boss can't really damage you, as all he does is true damage. Sentinel Onyx Son Singularity Gives everyon an Accuracy Up buff (super good with LoL's Extra Turn change), removes enemy buffs, revives fallen allies, and with Singularities, he will continually steal the shields the boss Cyborg gains every turn.
(but now i can actually do the dungeon... the loot drops kinda suck hey? other than the fragments, it's very rare for anything worthwhile to drop. like why would i want some colourless xp shards? is that normal for event dungeons?)