The problem with this is that they still haven't changed the rendering priority on A, let alone S rank, elite marks. They are swarmed as if they were Odin or Behemoth, but they aren't; the HP isn't too big of an issue but the rendering priority is. At some point, I was one of the first few people to spot an S rank, yet it'd disappear off my screen because of player saturation. By the time I do see it, it's already lost around 20% of it's hp; not counting the times it'd disappear midfight.

http://imgur.com/a/ira6h#5

Look at my position on the mini map and the timer (eorzean time) and can get an idea on what's happening to me here. My entire party was one of the first few grousp to get there, yet we only got partial credit because all of us (including the PS4 players) had rendering issues and could not attack the mark at some points.