I know/saw that 5 shams can do any heroic
I know/saw that 4 sham and a pally tank can do any heroic

I haven't heard or seen a team of pally tank, priest healer, and 3 locks doing heroics. Is it just because everyone is just doing 5 or 4 sham teams? I was thinking that this team would be able to do it better then 4 or 5 sham just because of the aoe. I know that shams have totems and chain lighting, but chain lighting has a cool down and can only hit 3 targets. With a 3 locks you have 3 seeds that hits multi targets all the time (while with the 1.5 sec cast time), which is great for trash but when bosses come it is only a single target. Just wanted to know if my team can do heroics when they get to 70.