Patients needn’t seek treatment from only those physicians suffering the same condition nor are only plumbers whose faucets leak qualified to repair them.
You wouldn’t go to a doctor who wouldn’t be able to heal himself or a plumber who couldn’t fix his own leaky pipe. The fact that the doctor is well and that the plumber’s pipe isn’t broken has no negative implications as to their abilities. In fact, perhaps it indicates that they are good at preventing problems.
Perhaps one should seek out only those counselors/rabbanim who have themselves gone through divorce?
No, that would be moare analogous to a plumber who couldn’t fix his own leak.