@eel5pe

I have done the content on the PTR and, well, I also happen to have played the raiding game since before time itself. Yes, totally, I'm like that.

In all seriousness, that's merely how balance works. Going from Ulduar to ToC was a slight challenge for non-heroic guilds, but it was totally do-able. Going into ICC from normal ToC was possible, but it was pretty tough.

During the time of ICC's release, I raided with two guilds. One which was clearing heroic content, and one which struggled constantly on heroic content. The first cleared through ICC normal was minimal learning difficulty. It wasn't overtly difficult until we hit the later tier of bosses such as PP, Sindy, and LK, but it wasn't a walk-through-the-park either.

The second guild managed to clear all of the same content as the first guild, but it took a lot longer. It took us two nights to initially clear out Saurfang because we didn't have the healing or damage that we needed. On the second night of raiding we managed to get it down, but it wasn't easy.

Every raiding tier is balanced on the assumption that you have gear from the prior raiding tier. The bosses will be "easier" in terms of overall mechanics than heroic T11 bosses, but they'll be about the same in terms of overall damage. Get it? Like, the bosses will deal around the same amount of damage as you experience on heroic Magmaw....but there won't be that additional add there -- which, overall, makes healing easier. Tuning wise they're the same, the requirements for coordination and crazy stacking, they aren't.