1) He thinks shit went wrong at WotLK when they started making easier modes and encounters, for raid content to become more accessible. Exclusivity was key, to give players a feeling that there's more stuff they didn't see, to make the game feel "endless" and more immersive as a RPG. He explains it with the difference of changes that players want and need [that's the context of the thread this is posted in] - players wanted to see more content, but the feeling of exclusivity was needed (but not acknowledged by the hungry/vocal players, and ultimately the developers). Reading or listening to player feedback lets you see only the wants, it's hard to take decisions as a game developer because almost nobody voices the need - that's also why developer to player communication is necessary, to explain why changes being made are needed. Development is about balancing between these two.
2) This has little to do with balance or difficulty of content, and his reply to people complaining about game difficulty is this: "that's the lens of your personal values - you believe your values of game-playing (skill mastery) is the reason all players should play the game. Many people play the same games for different reasons." The same applies to changes like 40man raids and others. Furthermore, only a minority of players even engage in raiding at all, but even that lost it's exclusivity. He's disagreeing with the design philosophy at a higher level than things like these.
3) He respects Blizzard and GC in particular for doing all the dev->player feedback almost single-handedly, and says WoW is a well-crafted game, he just disagrees with some of the design philosophy and doesn't play it himself any longer since ~WotLK. This isn't a case of #shotsfired.
This is through my understanding, and I happen to agree with all of this. This exact subject was raised and explained many times before, anyway, even back when they introduced normal/heroic modes people already said that "I didn't see everything yet" is a much stronger motivator than "I want heroic ilvl gear". Sunwell is largely considered to be the best instance in WoW, ironically only 1% of players have seen it - a lot more just talked about it. The potential adventure was much more important ("needed") than Blizzard acknowledged, and they introduced LFR on top of it to make things even worse.
It's appalling that a game that's supposedly driven by content is spoonfeeding all of it's content as soon as characters reach a trivial gear level (LFR entry req). Heroic-only bosses are a bandaid, if anything, they just highlight this problem.