a derp build is a build that wouldn't normally work but you found a way to make it work for casual play... no hardcore raiding builds ... just builds that don't make sense but somehow work
mine is leveling frost dk as a tank in dungeons, full tanking boa duel wield parry swords spamming howling blast while keeping conversion up.
http://www.wowhead.com/talent#kx^N|osm