The issue nobody wants to address

[Colorful]

Because when I speak of following a DPS' abilities, I mean every single auto-attack, action, and step they take. -rolls eyes-

So what exactly are you looking at, applying dots and making sure they're not just sitting there doing nothing? Yeah, that will definitely help a lot when a DPS check is being failed and definitely is identical to a parser in function to finding out who is performing poorly.

Edit for your edit: Fair enough, I'll take that you're far more skilled than I am if you're able to do that. I struggle to watch other DPS while performing mechanics and my own rotation, but that does not invalidate a parser. I don't know the high-end healer playstyle of FFXIV, but if there's downtime I'd imagine you're able to keep track of everything, but a DPS that has the shortest (or close to the shortest) GCD, while weaving in OGCD abilities and mudra while trying to deal with the lag that comes with that, on top of performing mechanics it gets a little hazardous. It would be downright impossible in MMOs like WildStar and maybe even in WoW. But regardless of all that, my point was a parser would be a very simple way of going about it. Not only can you measure DPS, you can measure HPS, overhealing, aggro generation, damage taken from avoidable attacks, etc.