I love speed Runs. I do them both on my White Mage and my Scholar (So healer is relatively irrelevant).

The only gripe I have about running DF (WP) Speed Runs is:

A) Tanks assuming they will speed run (When they are fair fair too undergeared for it)
B) Tanks assuming they will speed run with a not-optimal group (Two monks? Sure why not!)
C) Tanks that fail to avoid the ground mechanics of the various mobs (It can be tough enough healing you through 7-8 mobs, taking that much extra damage is a surefire way to wipe the group)
D) Basically I blame tanks for any failed speed run.