Credit goes to Mxxxx2 for the idea, worked wonderfully!
/ dry_marsh_challenge_2_...
Small notes:
Do reset upgrades like Mxxxx2 says, try and do the challenge early before grabbing gemstones upgrades.
Dont pick Vitality unless you need the full heal, Vitality will increase your MAX HP, thus, every kill will do more damage (5%Max HP)
If your DPS is not killing enemies (You are not gettign XP), go ahead and get 1 enhancement (+10% Dmg) or Wings (+10% Spd) and see if its better.
Do grab Evasion,. HP/SP Regen, Study but NOT Buckler (Defense) since it comes with Retaliation.
I won on my 5th or 7th try, so check it out.
Good luck!