You might be blinded by the past, but Wotlk heroics was just as easy as these. Tanking them with ilvl 378 shoulders is nothing compared to what you could do with TBC gear in Wotlk. Naxx was first cleared in Sunwell gear and T6, and same thing for heroics. It was pitiful. Sadly, they pulled it again.
Boy I think I know what Warcraft is all about more than you do. It's Warcraft, it's about Horde vs Alliance, not bashing some weak prick who thinks he can shit while he gets his ass kicked 4 times and ultimately dying due to the weakest plan in Warcraft history. Sacrifing ALL of his damn minions to try and raise 10 (or 25) adventurers while he keeps the wielder of the Ashbringer alive right behind him.
The dungeons were just as easy as now, the raids were even easier than the normal dungeons, forgettable zones like Sholazar, Grizzly Hills, whatever that eastern place with the vrykul was called and Boring Tundra. Icecrown only hold credibility because its name is important in the lore, and Storm Peaks was the only good zone, which I have to admit could very well be the best zone in the game.
2 new bosses at release with 12 rehashed bosses. Another raid in the middle of it that included 6 filler bosses that you had to do 4 times a week, and two big raids with atleast 6 filler bosses too, I'd go as far as saying only LK mattered in ICC. All of them you could fall asleep doing and wake up 3 hours later to have the raid completed for you. Only difference with heroics this time around is that we don't have pain-in-the-ass heroics like Halls of Lightning, Stone and Reflection, Pit of Saron, Forge of Souls, An'kahet and Utgarde Pinnacle, which weren't even hard, just time consuming and frustrating.
And what do you mean with the way they dealt with LK at the end? It was probably his best moment, which is really sad. He was a big pile of unthreatening poop all through the expansion, getting his ass kicked continously. His lines were ripped straight from some 1960 Spiderman villain while his voice was that of Dr. Claw's from Inspector Gadget. They also further ruined Anub'arak and Kel'thuzad by fucking their voices up, and fucking up Anub'arak every way possible.
I don't see how that outdoes the Horde and Alliance war, I'm sorry, but you're not really getting what Warcraft is about. It's not about taking down the big bad, it's about two factions clashing against each other, Mists gets that right waaaaay more than Wrath's very rubbish lore did.
Also, the fact that you said you had only tried Mists on a friend's computer puts your opinion at question big time.
It never was a sandbox game, that's games like Minecraft. WoW have never been a sandbox game, there's always been a linear path as to what you're supposed to do in the game, started with downing Ragnaros, and then they've just expanded.