Just because some crappy fansite says so, doesn't make it true. You will not be killing the Lynx, or the Hex Lord in a few kara epics, you won't have the necessary dps. Badly geared tanks will be shredded by even the first boss and those with little more than Karazhan experience will find the instance nigh on impossible.

This is akin to those who claimed Naxxramus was doable before you'd even finished BWL, yet all they were able to do was scrape through the first couple of bosses, if they were lucky.

If you're gonig to do instances that are above your level of skill and experience, then be ready to deal with the consequences. ZA loot is Tier-5 equivalency in many places and as such, the bosses are Tier-5 difficulty. I'd go as far as to say that several bosses within TK and SSC are in fact easier.

Except for the first 3 bosses in Zul'Aman, Zul'Aman is much harder than Gruul, Mag, or SSC. It will be a few patches and many nerfs before Blizz makes it possible for the average "casual guild". Until then it will be extremely challenging.