I have to admit, I am confused about "Look Out Sir!" rule in 6th edition.
When I first read the rules, I thought that the intended interpretation was that if your squad leader was about to die, then you can potentially (on a die roll that is) make a different member of the squad perish instead.
Now, I'm reading that this will only happen if the squad leader takes a hit from a blow that allows no save (e.g. lascannon shot to the head; powerfist to the big toe; and so forth). i.e. this transferral is done before any saves are rolled ... rather than you try to save the squad leader, fail the saving throw, but someone else in the squad jumps in to take the death-scene instead.
It strikes me as a classic RAW (rules as written) versus RAI (rules as intended) conflict ... except I'm interpreting what was intended, rather than GW telling me what it is!
This rule may well need a quick FAQ ruling from Games Workshop to make it 100% clear. Whilst I agree that the people interpreting it as saving the squad leader from that lascannon shot are correct (RAW), I just can't yet get past my own RAI interpretation (yet). Of course, this might all go back to the first rule in the new rule book ....!