Block might be an RNG but it is also a tool which reduces healing required, which each healer will appreciate. Besides paladin has Bulwark which makes block almost 100%. Holmgang is very bad skill, if you are forced to use it and it actually takes effect (you would die without it), then you probably wiping anyway.
Also WAR doesnt have anything like Sentinel, other PLD cds are better than warrior versions, because PLD traits increase their duration and decrease cooldown, in boss fights PLD and WAR mitigation are similar for predictable damage, however PLD can mitigate better very high hits due to sentinel and Hallowed ground. In terms of mitigating unpredictable damage like big trash pulls, PLD rotating CDs will survive more and longer than WAR.