AFAIK you can't get a fate reward unless you synch. Yes you can heal players participating in a fate without synching yourself, but you can't win anything from it.

Fates do suck as a healer though due to the limited damage potential and SE's oversight that healing enmity doesn't contribute unless you deal damage as well. This is especially true for WHM since CNJ is a "healing" base class (while ACN is a DPS base class for SCH) so WHM will naturally have the most difficulty of all the current jobs.