The last level suggested TP is 5500. That kind of makes sense that they’d do that when you consider what a team of double costumed, limit broken, fully emblemed S1 heroes might look like (all real numbers from beta):
Hero Costume: (Attack / Defense / HP / Power)
Khagan Chief of Leopards: 994 / 916 / 2029 / 1039
Magni Ancient of the Underworld: 1035 / 872 / 1976 / 1035
Vivica Omnimend: 926 / 1022 / 2036 / 1037
Elkanen Lunar Spear: 920 / 1105 / 1893 / 1038
Quintus Love Doctor: 1035 / 888 / 1982 / 1039
Total team power (all with level 29 mana troops): 5533
By the way, that team is not a very good defense team (no synergy), so no surprise that so far it is losing defenses more than 50% of the time. I think any wins probably correlate with whether or not Quintus fired. When he does, it can be pretty decisive.
As to the new and anti-improved event itself, I was able to beat it with a rainbow team that is just under 5100 TP (my current autoplay farming team): MN, Morel, Elizabeth, Hannah, Prof. Lidenbrock. But definitely not using autoplay!
As of the 13th level, even with Hannah’s attack down fiends on him, Joon was able to hit my heroes with a hit that put out more damage than their max health, so guaranteed one-shots if you don’t overheal. By the 15th (last) level, slash attacks from the mobs got up to over 500 HP each and the bosses were easily double.
I beat the last level by using time stops to ensure the bosses didn’t fire much (one did sneak through after an unlucky endless cascade). I only used one antidote, one tornado and three time stops, so I didn’t need very many items. A well-synergized mono team should be able to beat the level even easier and quicker.
So while it was annoyingly difficult, it was far from impossible. I’d estimate that for many players the Omega (aether) trials are probably harder, but it depends a lot on roster options. Hopefully that info can help folks gauge how hard it is / isn’t.