With over 11.5 million subscribers worldwide, Blizzard's World of Warcraft is perhaps gamings' biggest success story today.

But it's not perfect.

Blizzard lead designer Jeffrey Kaplan, who was director on WoW and is currently working on an unannounced Blizzard MMO, described mistakes in WoW that Blizzard hopes to fix. In his GDC session titled, "Directed Gameplay Within World of Warcraft," he recounted the mistakes in WoW, specifically related to quest design.

The Christmas Tree Effect: This is when a player shows up to a new quest hub, and his or her mini-map is lit up like a Christmas tree with new quest opportunities. When a designer dumps so many quests on a player, it may appear that he's giving a gamer more options in an open world. But gamers can easily lose direction and a sense of purpose. Some direction from the designer is needed. "We’ve lost control of designers to guide the player to a really fun experience," Kaplan says.

A variant of the Christmas Tree Effect involves a quest giver that has too many quests to offer. Players just end up vacuuming up the quests with little thought.

"Too Long, Didn't Read": That quote comes from a WoW forum post referring to quests that are too lengthy in their descriptions. “It’s great to limit people on how much pure text that they can force on the player," Kaplan says. Blizzard's quest editor limits the amount of characters to 511.

On a related note is what Kaplan calls "Medium Envy," which describes when long-winded videogame writing appears to want to be like books or films. “We need to stop writing fucking books in our games because there are lots of better books out there," he finds. He's not against story in games, though. “We need to deliver our story that is uniquely videogame.”

Mystery: Mystery is a bad thing, as it means the player doesn't know what to do. An example of a bad, "mysterious" quest would be, "Something’s wrong in the forest, go figure it out." When players aren't clear on what to do, they become confused, and that provides for a bad game experience.

Poorly-paced quest change: Kaplan described a long WoW quest that is impossible to complete until the player reaches a certain level. For players below that level who are failing at that quest, frustration sets in, which leads them to lose trust in the game's design. This also leads to frustration, and a bad experience.

Gimmick quests without polish: These are quests that are more fun for the game designer than the player. Kaplan described a vehicle quest in WoW. The game's engine isn't really designed for vehicles. If it's only designed as a gimmick, it's probably not really fun for the player.

Bad flow: This occurs in WoW when players are given an inordinate amount of collection quests or kill quests in a row. It gets boring and repetitive. Kaplan laid claim to the design of what he called the worst quest in WoW, The Green Hills of Stranglethorn. Players have to find pages of a manuscript in a jungle by killing enemies who drop the items. Problem is that there are a lot of pages to find, and a very low drop rate. In such quests, players are pulled out of the experience and begin to wonder why exactly they are performing the action.

“You never want the player to think that somebody made the game. Every time they’re thinking, 'Why is this happening?', you have failed.”

Kaplan ended with a little food for thought for GDC attendees: “Every little decision we make as designers has a direct impact on players. It’s not enough for designers just to put stuff in games to see what the player does. We have a constant responsibility that gameplay needs to be fun."

He says that giving gamers a strong sense direction shouldn't be considered dumbing down a game. "This is not over-simplified hand-holding, it’s elegant game design.”

Sande Chen contributed to this report.