You get them from BBI. They are augments that once you unlock them, you are able to apply them to both your character and your pawn. So far the only one that I've found to be of any use is Tenacity. It puts you at 1 health any time you're hit with an attack that would drop your health below that with a massive hit.
I know that Sorcs do well against Ur dragon, but have you played a Magick Archer? I don't know if a Sorcerer is "the best" at killing Ur, but they are certainly one of the best.
I also don't see how our Sorcerers "go completely different routes". They aren't that dissimilar (what are these "status spells" that I supposedly take that you don't?). The only thing I don't do is carry around more than a single "giant" spell, because aside from flavor, Maelstrom and Bolide are too similar in outcome.
I haven't played a Sorcerer in BBI yet, but Voidspell did absolutely nothing at all in vanilla for me other than to cure petrification. Did they change it? Because it was supposed to remove all kinds of status effects, especially those that affect stats (curses), but it never seemed to do anything at all other than take up a slot.
The whole Fire > Holy was not in regards to usefulness. It was just that you don't actually get Holy Affinity right away, and Fire is more useful starting out. Holy doesn't really do anything against Ogres and Cyclops either. Once you're near the end of the game, and especially post, it's either Ice or Holy. I don't really spam the charge attack though on most enemies. It takes way too long to charge just to kill one enemy at a time as opposed to simply casting a multi hitting spell that will kill more at once and that has a similar charge time. I can't remember the last time the Holy bolt actually hit more than one enemy at a time.
Yes I've played every class. And yes sorcs are still the best against the Ur dragon. I can endless stun lock the ur dragon, something that I can't do with any other class. MA are better in certain aspects in BBI though.
I don't bother with Miasma or the rest that give debilitations, that's what I mean with the status spells. Maelstrom and bolide are only similar in the fact that there's some sort of AOE, but maelstrom is dark, which is a useless elemental, and the main damage it causes comes from dropping enemies which can be picked up. That means it's useless against hydras, orges, dragons etc, and it's terrible to use indoors.
I find voidspell essential in BBI, but yeah it's mostly useless in vanilla because very few creatures can cause petrification or str/mag lowering. In BBI, those worms, garm, cursed dragon can all do these. Anything that voidspell can't cover, halidom covers, so they make a perfect status defense.
Fire is better starting out, but nothing beats holy. And holy focused bolts tears cyclopes up, even gorecyclopes. Focused bolt is way faster than casting any spell and because you can 1) move and jump while charging and 2) recover stamina as you charge with it, and 3) you can cancel the recovery animation. That means press and hold X, jump to cancel the single shot animation, release X and instantly hold it again to shoot and charge, and then jump again right after the shot to cancel the recovery. You should try it against a mob some time. And just watch the exp keep ringing it in after just one shot.