One single blade is all you need, along with a back-up on you, either for real life battles in our real world or whether it is (most likely) the same in the Star Wars Universe. (Lightsaber, vibrosword or vibroblade, etc.)
There are several technique's used for disarming someone with two blades and some of those technique's are quite unusual. The old saying that: " Two blades are better than one."
doesn't compare to a highly skilled Blademaster with one blade in hand.
Oh...and BTW, you keep a second blade on you just in case you happen to get disarmed too.
(A short blade would be ideal.)