I play PLD and I can say that my dungeon boss opener is:

1) Shield Oath
2) Fight or Flight
2) Shield Lob (to pull boss and generate some agro)
3) Circle of Scorn
4) Flash x1
5) That one OGCD attack (I think its green)
6) standard attack
7) Savage Blade
8) Rage of Halone
9) Sword Oath
10) DPS combo your heart to the rest of the fight as you should not lose agro at this pint unless you are really under geared compared to your teammates.

https://www.mooglemedia.com/paladin-guide/