Ok first off those numbers are useless. Thats not a success rate of guilds its a wipe vs kill rate. So 40% basically just means that people are wiping 2-3 times per time they kill it. Though again really people wipe more at the beginning so that number is going to trend higher the longer its out.
But you aren't wrong. according to http://www.wowprogress.com/ it looks like 29% of guilds have cleared all normal modes and about 1% Heroic clear. Which sounds about where it should be.