I agree. As a melee player, I felt that the launch heroics were perfectly tuned. Well, mostly. I had a blast whether I was running them with guildies or LFG pugs.

Many casual players are much better than people give them credit for. I'd offer the following explanation: 1-80 content essentially trains players to believe that standing in fire is an acceptable risk that is worth the reward of maintaining top-dps, that CC is irrelevant and just slows down the dungeon, that interrupts aren't necessary, and that healers don't need to worry about mana, and tanks don't need to worry about blowing cooldowns in damage intensive moments.

99% of the game trains new players to develop bad habits, and never learn good ones, and the last expansion (WOTLK) made lots of old players unlearn good habits and learn bad ones. Suddenly you hit Cata dungeons and everyone is expected to play like it's TBC heroic SLabs again, even though the game hasn't had that kind of playing experience for years. You can't expect a player base to spontaneously change like this.

Why not?

Vanilla and BC expected a pretty drastic upgrade in play quality at endgame. Like for all of wows history except for wrath getting through dungeons and heroics was kind of an accomplishment. Why can't we expect that going forth, why do can't we expect people to go into a dungeon and prove they deserve to finish it.

No, many casual players really are awful. Yesterday I was in a group with a level 40 boomkin in half agility gear. He wouldn't cast spells until the mobs were half dead. At one point he actually melee'd. I told him politely that he would do three times as much damage if he would wear gear that only had intelligence on it. His response: "whatever".

You could not be more wrong about Vanilla. I distinctly playing back in the old Loch Modan a long long time ago in a patch far far away, where there were outdoor elite zones that required coordinated groups and liberal use of CC to even complete certain normal quests! That was the first time my first toon (a mage) learned how and why to polymorph. Until then I had thought the ability was silly and useless. After that quest I learned it was powerful and rocked-socks.

I also remember during that time-period that a successful clear of Gnomer or SM Cathedral was HARD, like absolutely incredibly hard for a little dinky 5 man normal.

Absolutely nothing like that exists or has existed since at least WoTLK. 1-80 is a faceroll, partly because of nerfs to difficulty, and partly because gearing up is so easy now.