So I just tested the following on live:

Click 1:
/castsequence judgement of light, crusader strike, consecration, crusader strike, exorcism, crusader strike

Click 2:
/cast <spell>

Where <spell> is, I tried Divine Storm and a raft of other spells. Nothing ever fell through to the second click button. I tried both a simple /cast macro in that button and dragging the spell from the spellbook. Nada.