That's understandable...but I don't exactly like it myself. Considering you're nerfing max exp gain in there to 30%....I'd be impressed if they had guys in the 800 range get passed wave 90 or so. Anyway, it'd be wierd for someone to get 600 in one trip. I expect you'll have AoEs and chains and all sorts of stuff that'll keep the weak guy from getting that far. Just be mean and kind at the same time. Do it a way nobody would think of (except for those dedicating themselves to ideas)
Basically: If someone is outside of the 100 level range...all the creeps focus on them. They'd ignore the level 1.3ks and go straight for the 30s. The most they've got is 1k armor (cheese shield/armor of gods) or perhaps even chronos stone if the person was nice (woohoo....10k hp?)
From that they'd have around 1k armor and 10k hp, and from the massive barrage of attacks against them, I doubt they'd survive long (unless it was a tank or healer)
That way people have a chance early on to get some levels from someone trying to level them in struggle (I'd personally set them up at medeans) but I doubt they'd make it half way through. Even if you had 3 PRs I doubt it's possible, simply because they've all maxed out their crit items, and don't hit multishot on those attacks. If they drop their crit items, they have nowhere near as much DPS, and can still crit from skill.
lol
