Yeah but they are using quest guides to do specifically all the high experience reward quests and getting help from other players for hunts and money. They have also played for almost 5 days straight... I think they are just more dedicated than most of us and genuinely enjoy questing.

Casters still need con to not die. They need strength to carry things. Plus most casters don't use spells 100% of the time. They still use melee combat as well.