That's the downside to these rerun events. I wonder if we're gonna get another lottery event sometime cause so far ObFes is the only one. It might be another summer event or a holiday event though cause the premise behind this event was a festival where a lottery would fit as a reward mechanic.
I'd be down for more lottery events just that I'd prefer if we didn't have to farm a currency as stamina to farm the lottery currency. Just have a separate regular sanity consuming stage to farm lottery currency. It's how FGO does it.
OF-EX4 is really hard. Keep getting my tail kicked even with strategy advice from Eckogen's videos. I got frustrated so I put it down for today.
Not sure what you're having difficulty with but my personal tip is either have more healing defenders (you can borrow a Saria since there is nothing to farm in the EX stages) and/or you can use Ceylon. Put her in the middle and her healing range heals everyone.
Btw, official reveal for Purgatory aka Lava Alter. Still an AoE Caster but she does have nice talent that increases the starting SP for other Casters. Could make nice combo with helidrop Eyja. Her skill 2 looks interesting to use. Also from that gif and in her skill 1, looks like we're getting some interesting enemies this time.