Otterman,
having been involved with one operators fuel conservation programme a few years back, I can rest assure you that block burn/hr was and probably still is the yardstick used. The bean counters argue that averaged over multiple round trips and routings, that block burn/hr is the yardstick to use.
Cannot say I agree with them. Merely by taxiing slowly I can push out my block time and appear to be all the more fuel efficient.