You realize it takes ~60 hours of runs to get full DL gear if you are speed running it? People who run keep for tomes are going to run it the fastest way possible. It isn't an exploit. The dungeon was designed to make it possible to do this. The tank is pulling aggro and dying and getting raised, none of the mobs cast a heavy or binding skill that leaves him in place, so he just keeps running. An exploit would be if the tank could take a specific path and a bug in the game made it so he didn't pull any aggro, or was invulnerable, or there was a glitch in the wall that skipped you to a certain area. If you're going to fix anything make it so there are other efficient ways to grind tomes instead of running the same couple dungeons over and over and over and over and over and over and over and over (anyone who has done it realizes this goes on forever) again.