Resistances reset after a period of time. You don't have to die for them to go away. I'm not sure the time off the top of my head but I want to say something like 30 seconds or so.
Warrior does actually have pretty close utility to paladin, though stun locking is actually better than holmgang. While stunlocking one person might be a similar comparison you're looking at 4+ targets to take away from the fight for a max of 9 seconds at a time per player. Holmgang can't match that.
Paladin has Testudo however Paladin also has Divine veil, which they can trigger themselves now.
PLD> War> DRK , Dark knight has.. A heavy, a Damage reduction and a very mediocre stun for utility, they can also annoy casters with ranged attacks easier than the other two.
Paladin has way more utility than you're giving it credit for
