Yeah this should be tweaked. Just did a 40-50 where 2 people left on 49 because they didn't get any upgrades. Luckily the other person with me was a healer and got +3 so we were able to duo the boss. I'm not sure the final boss would have been possible as 2 dps unless one of us was a summoner or something.

Possible suggestion: Make clearing floor 50 give guaranteed silver chest drop from final boss, where the worst possible outcome is +1 to both weapon and armor. Low chance for +3.