So, since I was asked by a lot of people on how I beat the event and what I recommend, I will make a thread to answer most of these Questions and give some teambuilding advice.
I completed the event yesterday
Before I start I wanted to thank @Killerdog for having the patience to discuss possible lineups in the week before the event started. I know I had a lot of Ideas 
So heres my team:
Its basically three teams.
First of you have the OoO team. Its the one team best suited to survive. Even on Floor 90 and above it can survive more than 5 Floors on its own. Of course it also comes down to luck. You will find yourself up against a lot of awakened mythics, DR, Camo and sleep immunes from Floor 90 on, so you have to carefully fight your through. Don Rilla is a key monster here because he can get rid of the camo or sleep immune monsters before they can harm your team.
Then theres the Frost-Soul team. A classic setup known from the early days of neo. I support it with Aegis, Heavens and Shiva to keep it alive as long as possible. Bascially you OoO with Frost and switch place into shiva. Then you wait until the enemy monsters die and heal your own stuff with Aegis and Heavens.
Third team is stun + Delugazar. Very powerful but also very fragile. Buffs are quite significant on the higher Floors so monsters without HG can be taken down with two AoEs from strong monsters. Nulltron helps to get rid of the stun protection. Then just stun the lineup into oblivion and kill it slowly off.
Mistle is a sub for Aegis
Blazebones is a sub for Heavenswyrm or a dying sleep immune monsters
If you want to follow this pattern here are a few alternatives if you dont own certain monsters:
Oniblade: Actually only Stratusstrike is a proper replacement. If you have all of the other powerful sleep immunes you could try and use an Epic OoO but it will be a lot harder with that
Bunker and Rilla: You should own one of them tbh. You can replace the other with Diredemon if necessary. Not a 1:1 replacement though.
Gallio: Difficult. Theres no replacement for a stun flash that fast. If youre using stratus you can use Heavenswyrm because Stratus is a bit slower anyway. If you have neither you could try galvbane to stun a monster out of the way that would have been faster than your OoO setup.
Heavenswyrm: You wont get this combo of speed and healing anywhere else but Willowyrm can be a replacement and provides additional stun protection.
Frostrider: Theres no proper replacement for OoO + Switchplace. However if you change the setup a bit you can Use a OoO monster, Jackalhotep, Soul and Aegis/Shiva. As you can see you would have to swap out either Aegis or Heavens then. So thats the downside.
Soulstealer: Hes vital for that setup. With a bit of rearrangement it could also work with Onigeist.
Aegis: Can be replaced by any HG Auto Protect but none of them is a 1:1 replacement due to the lack of healing abilities.
Mistletorment: Titanmoth can be an option but it lacks the healing of the awakened version.
Poloarboss: Really crucial. Quick stun, crescendo + healing + reinvetrograte self.
Novadrake: Crucial again. Low TU attack, healing, plus that super useful stun flash. No other monster will offer you this. Not even close.
Delugazar: You wont find this power anywhere else but a sweeper that can be charged with timestrike or timestrike double would be a good start to look for.
Nulltron: Stunpulse + Repulse is super useful. But you can use Galvbane here aswell.
Blazebones: Hes unique but not crucial for the team. You can replace him with other useful monsters for dungeon challenge. Just make sure it fits in the part of the team you want to use that monster.
Shivadragon: Probably the MVP for this event. Cant think of any replacement.
In Case you want to try to get from 90-100 I would advise you to save your strongest team for the last floors. I tried to get to 95 with the rest of my team and used OoO from 95 onwards. After a few tries that worked.
If you have questions feel free to ask me.
Cheers
