I played about 30 heroic sivas and only got 2. So last night I did a couple of 320 sivas and got one, but it dropped a class item when I needed an artefact as mine was 7 levels below all my other kit. So i tried again today on 320 and got another in the second strike of the day. SO that's 2 in 5 - can't be right to get 2 in 30 on heroic but 2 in 5 on 320??