The combination of difficult quests, experience loss at death, and unavoidable player-vs-player violence means that despite systems like villain points and an in-character way to declare Player-Killers "wanted," the necessary battles are more frustrating than they would be otherwise.
You can set your clock by opportunistic players coming to attack while you try to chew through yet another limp quest. As a result, single players are doomed: questing groups have already begun simply attacking any solo adventurers they see approach, under the theory that anyone running solo is just out to player-kill.
Beyond the constant necessity to churn kills of either monsters or players for some experience points and release from boredom, design and technical issues clutter ArchLord. There are eight different classes, but they all fall into one of only three basic roles - warrior, archer, and mage.