I came up with a build idea. To set you in the theme, here are the goals of the build: max out his own xp per minute at the detriment of others by just standing at the front door, AFK.
Now on the build itself.
You NEED to be a wizard and be able to cast extended hastes. Now, how good is haste if you stay at the door you say? well, you cast ONE haste at the beginning to get the party started. If the group you're in can't finish the quest before your haste expires, they are noobs and you shouldn't waste your time with them to start with.
I know this is a pretty vague build, but hey, if you really intend to be a piker, you can make a few mistakes, people wont really notice you are a gimp piker.
Have a good day!
EDITED the build.