I pretty much agree with what everyone is saying. Definitely keep Halo. That song is mind-blowing live. Old on the other hand... maybe I've seen it too many times but I'm over it. Probably my least favorite song off Burn My Eyes at this point. Struck A Nerve belongs in there over several songs to me also.
My theory on Darkness Within is they plan on it being their US Single release before the US tour so it's going to be in there every show. Be Still and Know & This is the End would be way better live to me but I see what they're doing. Hopefully they work those 2 in by the time they get to the US.