Why mark targets?

[Jyoeru]

I actually really dislike macros like this. All it takes is to accidentally double-tap and it's gone, or if you lose aggro and provoke+shield lob a secondary target, suddenly that one's #1, etc.

I double tap all the time. GCD allows me to tap once more without wasting usage on the ability, yet reestablishing the marking icon. Just takes practice.

I can't speak for PLD. Maybe it's not as great for you guys. And it really doesn't matter if you switch that 1 mid-fight. I have accidentally done that, too, and people don't usually switch their focus target. Even if they do, it's never proven to be the end of the world. All that matters is what people are attacking the first 15 seconds of the fight, to be honest.

(Not including adds. People need to know when to attack adds, so that doesn't really apply to this point in the discussion).