I'd still contend that if you win a single healer GCD by taking Mantra it'd be better (e.g. one Broil, where I can do 1800 damage in questionable gear). It is difficult to use, of course; your healers have to think a step ahead, so you'd be having to think two steps ahead, plus 5% is really hard to notice (people who worked on That Other Game many years ago once determined that people need about 1/8 more performance to really notice differences), but if you really root out where the heals can benefit from a boost, you can probably find a gain just as esoteric but with more damage.

Anyway, as of 3.5 we don't lose that last-second 4th hit apparently. PRAISE THE SUN