well to get rid of the problem of casting corruption over and ober again use this instead for your lock:
Code:
/assist main
 /petattack
 /castsequence reset=target Corruption, Curse of Agony, Immolate, Shadowbolt, Shadowbolt, Shadowbolt
only small fix, but with using the assist directly with the name of your toon, you do actualy not change your target at all, if your main don't change it, and thus the reset=target is not triggert everytime.