I guess that is true but you also have to think about angles with dual wielding a lightsaber per say, you can get a lot of angles and you could hold your own against multiple enemies. double bladed you can do the same, (like seen with darth maul in the first movie) but he used ways to take a break and get away, dual wielding you don't have that much of a problem cause of the mobility you have over it, but all you said was very true.
P.S. dual wielding lightsabers don't have to be the same one can be a shoto and another can be normal (like Ahsoka Tano)