Level 2 is super brutal yeah :( I just spent 20-30 minutes trying to beat it again and couldn't haha. I have managed a few times before though.
The way I beat level 2 is usually with two archers in the middle area so they get maximum value. I stay as greedy as possible maximizing my economy early on, kill enemies only at the last last moment possible, and only kill one of the first two mails and survive the hit from the second. The mails usually have only 50-80 HP for me though, which could be affected by clear spead but also maybe it's just a problem with my game's clock :( sorry if it's kind of a bug, it's not impossible.
Edit: That's not necessarily a good thing I realized but, actually, there's really no advantage right now in killing monsters early. Always prioritize the economy when you can.