Because the guy who's dead isn't cleansing anyone.

What I did was make a castsequence like this:

/castsequence [target=Chernabog] Cleanse,,,,
/castsequence ,[target=Hilal] Cleanse,,,
/castsequence ,,[target=Hubal],,
/castsequence ,,,[target=Illat],
/castsequence ,,,,[target=Taalab]

And then changed the names in sequence. So, the first guy starts with Chernabog, then the next guy with Hilal, then Hubal etc. It works perfectly. I can just spam it and it tries to Cleanse every member. If there's anything Cleansable on my guys it goes into overdrive and gets it off in a single global.