Well, there has to be a reason for Vader to state in ANH: "THIS time nobody will stop us." - Perhaps the thing seen in ROTS was blown apart long before ANH.
I would also think, that the plans of the Seperatists have to be re-designed, since a Seperatist-DeathStar would be suited to their kind of equipment (droid-fighters) and highly automated (again droids), but with little facilites for millions of living beings.
The optimist thinks, that we live in the best of all possible worlds and the pessimist is afraid, that this is true.
"Don't ask, what your country can do for you. Ask, what you can do for your country." Mao Tse-Tung.
