Droidekas are savage, and excellent point defense units. Assuming there's a screen of smoke or suppressing fire or something to cover them as they roll into position, they also make highly effective assault units. They have their weaknesses, as do all things, but assuming they are used properly, they massively outclass SBD's.
SBD should lose its shields, as not only are personal shield generators extremely rare, SBDs were also all about higher hull integrity. They were supposed to be durable in contrast to the flimsy and weak Battle Droids. Droideka have decent hulls, but vastly inferior to the SBD; their strength is in powerful deflector shields.
Armor on PCs directly fights against Firepower - why wouldn't the Droids/Entity act the same way?
Couldn't we have the Hull value remain "Droid/Facility HP" and add on an Armor value (I guess like for Creatures - though that isn't really used currently) that reduces damage done to it across the board and require a higher firepower to attack it successfully. EDIT- Wait, the Ground Combat Rules say that already happens, with an intrinsic "damage reduction" value. That value ought to be, but isn't currently, listed on the rules pages for the specific entities. Which Rulespage is out of date?
Likewise for 'shields' for those who have shields; that is, shields become a 'limited-use' armour type, such that either doing the mass cumulative damage over time (like it's set up for now) will deplete it, Or having a high enough firepower to bust straight through shields will deactivate it for the round like Armour.