Regardless, the saber staff was very effective, on the defensive it could block as quickly as a single-bladed weapon, but with only half the exertion, on the offensive it was deadly, it could tire out an opponent very quickly, which is exactly what Darth Maul's tactic against Qui-Gon was.
While yes, it does limit the potential range of the weapon, it is fully possible to fight with a staff in the real world without beating yourself to death with it, even if you are restricted to holding it within a foot to either side of center. Therefore, it should be possible to fight with a saber staff without lopping body parts off. Especially with the predescribed access to such a power as 'The Force' to assist you and augment abilities. Besides, if you listen any time someone describes a saber staff in canon, the general reaction is that it's by far the most retarded weapon a Jedi could carry. For example, in the book Darth Plageuis, Palpatine and Damask have a conversation regarding Maul's use of a saber staff, where Damask states that anyone using that weapon must be out of their mind (or something similar). When Qui-Gon and Obi-Wan see Maul's saberstaff, they both look confused. I attribute this to the fact that they are shocked that anyone would even attempt that weapon.
If you read Darth Maul: Shadow Hunter, the basic principles of the saber staff are revealed in full and bely any queries you may have about the weapon.
Then we have Exar Kun's own words on the weapon as well, which reveal that it can be used at such great speeds that an opponent would simply become confused and overwhelmed, only seasoned duellists with much experience could tackle the double-bladed Lightsaber and survive.