Hey Layla, my statics MT Pally keeps going Sword Oath during our DPS burst, losing hate to our MNK, DRG or MCH and wiping us to simple mechanics in fights we should be clearing. He has also started losing it to our WAR and refuses to switch. Do you have any tips on what we should do?

It sounds like you're not running a Ninja. He needs to accept that without a NIN he's going to need to do extra Halones and sit Shield Oath a little longer. Tanks are there to support the DPS - not the other way around. If he can't accept that, he won't go very far.
Harsh maybe, but it's reality.