It was harder than I wanted it to be, but
- healing immunity is a thing, and
- You only have to beat it once at 3*, then you sim it.
- Remodding is no fun, but if you drop on some GL mods it becomes much easier.
- It is reasonable to make it hard and/or expect players to remod if it's a one time challenge. I'd be less happy with the event if you had to play it again every time. I mean honestly it wouldn't even qualify for the name "Event" if you only had to play it one time and that one time only required any junk mods you don't care about and pressing auto.