Currently the Empire is disorganised, we had hoped Palpatine would not reapear for another six months or so. That would have allowed the Imperials to fully fragment and we would have been able to eliminate one War Lord at a time. If Palpatine has reapeared then we will have to find another way to win this war.
What War Lords? Those were the Separatists. Cracken annihilated them. (Or most of them.)
And the Empire is not that
disorganized, and the disorganization that is there is because of Reletha. Destroying Reletha would have (and will still) simply strengthen the Empire and allow it to finish reorganizing.