Step 1)
Get a strider, and an outfit normaly worn by nukers in PvP.
Step 2)
Run around besieged castle trying to get as many people as you can to chase you thinking you're a Necro/SpS and a Clan leader who's waiting for that perfect moment to sieze control of the castle.
Some healers are very slow, so strider is helpful if you are buffing people on the run or want to catch up your group runnign somewhere.
Combat situations are different story and mostly your strider won't help there unless you run off enemies. You can't use spiritshots being no strider, so you better dismount and wield your weapon if you are to heal/debuff.
I hear you regen mp as if you were sitting on the ground when you're on a strider. I haven't actually checked it myself, but I believe my source. Only really useful for rechargers, as you can't have weapon equipped when mounted.