Actually Mara had a small blaster with her too, but not the heavy duty guns the troopers were carrying. She did attempt to hit the sensors with her blaster fire, but it's shielding was too quick and it would activate it's shield before it got into it's tripod mode.   As far as short circuiting droids, apparently the droideka in Survivor's Quest was very tough, and extremely fast, and smart because it was reprogrammed. Eventually Luke and Mara destroyed the Droideka with a third lightsaber they had with them, by making the Droideka roll over it unsuspectingly and the saber was within it's shielding.  Then Mara used the Force to activate it and hit it's internal mini-reactor.   But I digress, this is about the Imperial Probe Droid which is nothing like the Droidekas and is also not as formidable. 

I had a show down with a probe droid on Endor map, it really takes a sustained amount of fire and a poor operator on the other end to kill it.  Get yourself behind a shield and use the heavy guns against it, it will eventually be destroyed if the operator stays in one spot.  But it is hard to see at times if the operator is good at hiding.  I really like it as is, though I wish it could move up and down a few feet above the ground and be a wee bit faster, like in Empire.