Regarding Sorcery, in terms of numbers: (and this is from memory as I haven't touched my Sorcerer in a few days now)
With a +3 staff and about 20 int, just past the second boss.
Soul Arrow did around 70-80 damage per hit.
Greater Soul Arrow did around 150-160 damage per hit.
Hilariously, Soul Dart did 10 damage per hit when I bought it after reaching Firelink, sure it's fast but come on.
The problem is that while Greater Soul Arrow does good damage it also has a 1.5-2 second cast time, making it basically unusable once you have an enemy on you. Soul Arrow too still has a close to 1 second casting time, so you're pretty much just forced to keep your magic as an auxillary damage source while you poke away at standard enemies. At the start it's not possible to be a full magic wielder, most of your damage still comes from your weapon. Maybe you could if you switched all your Estus to Ash, but then you'd have to play like some MLG dude and never get hit.