Magic-eating flying blobs: because monsters that disproportionately limit one set of classes are always fun! They come in two sizes, 'droplet' and 'sphere', which are respectively medium and huge.
Medium-sized outsiders with 3 HD. Ability scores are surprisingly neat, with +8 dexterity, +6 constitution and +4 wisdom, balanced out by -2 strength and -6 intelligence. Aoa's have a large number of defensive abilities, including +8 natural armor, DR 5/magic, resistance 20 to all energy types (except acid for some reason?), and 22 spell resistance. The latter also reflects any resisted spell back at the caster, and automatically reflects gaze attacks as well. 50 ft. (perfect) fly speed is one of the best movement types available at this level.
The problem: Aoa's are completely terrible offensively. Their sole damaging move is a 1d8 slam, they don't have SLAs other than at-will Detect Magic, and they don't have limbs. While the ability to Dispel effects on whatever their slams hit is neat, it's not terribly relevant in many combats.
Reading this, I'm genuinely unsure how those are supposed to be CR 3: the worst case is the party wizard failing to identify it and getting zapped with one of their own spells, followed by the fighter finishing it off while the others hang back. -0 LA, terrible PCs, not even worth it on niche ultradefensive builds.
Rarely does adding more HD improve a monster's PC viability, and these are no different. Just a droplet with bigger numbers, one of which is sadly HD. -0 LA.