About the EXTRA Quest of Jalter event

Seems okay-ish. Waves have low enough health to be cleared with area NPs. My team would probably look like :

Amakusa Shirou Tokisada, Arash with Kaleidoscope, Support Jeanne , then Cuserker to come in after Arash uses Stella.
(Equip other backline servants with + True enemy appearance to not face Jalter in the end?).

If Jalter does pop up in the end it would be a problem due to the double Ruler setup. But honestly going double ruler is the safest way of getting past the first couple rounds without a sweat, so that's just the price of doing business. Also, a grailed Cuserker is broken enough to take on Jalter, especially with stuns coming from the two rulers and the utility of their NPs.

Good berserker team should be fine, I guess

Berserkers
Their HP are trash mobs' tier, they'll fall after a few AoE NPs.
I don't remember this battle being so difficult, that you'll need CS, you'll probably be fine.

Well, then I won't be to clear the event as usual. It impossible for F2p to clear harder content in the event, which what I hate the most about the event. The only way to clear the main story do me is to max ascend my 3- star and lower servant, to be frank I don't care about overpowering via the story.

I'm probably gonna run my Waver-kun (Scholars of Chaldea) , CuAlter (Kaleidoscope) and use a support Scáthach as my front line. Backline will be Mash, and low cost servants to have each of them hold a Scholars of Chaldea!
The frontline should be able to clear all waves pretty easily by itself.