I just finished my first run in the new Zul'Aman instance, which goes live next Tuesday. And I don't want to spoil any surprises for you, but I do have to say that the instance is most definitely a gear check. Our group of players was getting slammed all over the place, tanks nearly one-shotted, DPS seemed to be running out of steam, and healers just barely kept up, and all on the first boss!
Given, the raid group was a PuG on the PTR, and that created some communication roadblocks and other difficulties that probably made things more complicated than they needed to be. Still, the instance does seem to up the difficulty level for 10-mans, even if just a bit for those that are properly geared. The under-geared in our group definitely had a very difficult time, however, and our overall performance suffered as a result. The impression I had (and do keep in mind that this is only my first) is that pre-Karazhan blues just won't cut it in Zul'Aman. And casters, an excellent Spell Hit rating is a must.
All in all, the run was an enjoyable introduction to what we all be will seeing quite regularly come next week. Oh, and when you do eventually venture into Zul'Aman, bring two tanks. I know, I know, I said I wouldn't spoil anything. But trust me. You'll thank me later. ;)