Originally Posted by Amroo

I've stated a few times that from a logical perspective it's most efficient to use BT to move your death rune SS one rotation up. That way you gain one SS every two minutes instead of 2 BS.

So basically your initial rotation becomes
PS-IT-BS-BT/SS-SS
SS-SS-BS-BS

You continue with
PS-IT-SS-SS
SS-SS-BS-BS

until the BT cooldown is up again and switch back to
PS-IT-SS-SS
SS-SS-BS-BT/SS

and then again until the next BT
PS-IT-SS-BS-BS
SS-SS-SS

This exploits the fact that if you use BT when you just used BS (so that one death rune is on CD) and your second blood rune is up, the death rune CD is reset and you blood rune turns into a death rune, such that you have two death runes to use immediately.

As for Bone Shield: If you cast it right at the start of the encounter, most encounters in ICC are either dead before the 5 minutes have passed or there is some time during the encounter where you can't dps anyways and just recast the shield then.