I don't have any targeting commands in my macros other than casting Misdirection on my pet.
I used to have this issue of my target switching to corpses and I solved it with a targeting macro:
The issue with this macro is that I end up pulling things by mistake. So I stopped using the macro and was fine for a few months. But now the switching to corpses is back.
Don't know if this is part of the issue but I'm using ISBoxer.
Has anyone else had this issue and solved it without a targeting macro?