You're really reaching as far as logic goes.
This has already been done 100x over, i assure you... If you'd like to feel extra silly, look at fusional, who was in the world first kill at that, and clearly played WoW through WotLK. The same qualities serve you well in both games - knowing how to predict, read & respond to encounter mechanics, knowing how to optimize your stats and ability usage, knowing how to optimize your position for highest action/inaction ratio, and knowing how to communicate. These are the pillars of raiding that won't change no matter what game you're playing.
You should actually read the whole sentence before replying - addons have nothing to do with quality of battle mechanics. Server lag essentially limits the speed at which the battlefield can change with things like damaging ground effects & area spells, boss repositioning, etc. At the same time there's a rich variety of battle mechanics that you don't see in this game yet - player centered area damage effects, bombs that need to be dispelled or healed off a target, prisons you have to break players out of, enemy heals & spells requiring interruption, player-controlled destructible environment, vehicles, split-front battles, the list goes on.
And as for your stance about good players having absolutely no need of addons, I've seen enough "good players" who've needed someone else with an addon to show them they were not doing so great to know that personal evaluation "by feeling" is far from incontrovertible. On that note, from personal experience playing MMOs for 7 years, it's a ways off the mark for the majority of people...
So how do you, as an invested member of the party who doesn't want to waste time, tell who's correctly evaluating their performance when the boss' (or any other encounter-critical monster) health is a mishmash of damage from multiple sources that you can't parse out by eye? Well, an addon that parses might be a good way... right?