You still haven't convinced me how exactly would dissolution of Imperial Intelligence benefit them in any way. Both in short and long term they lose a great deal of personal power and influence. Are you implying they are self-destructive or even mentally challenged?
What I'm saying is that a powerful sith might believe that they could bring at least some of the assets of imperial intelligence under their personal control, which would be of immense benefit to them. Power plays don't always work as intended, however, especially when there are wild cards in play as there are in the the agent story. It can be argued that the Sith are, in fact self destructive, in that they put their passions and personal power ahead of the good of the empire. They wouldn't see it that way, of course.