There's something glitchy about the targeting when it comes to magic.  Soul arrow specifically.  I haven't tried pyro spells.  Throwing items seem to function correctly so far.
 
On several occasions my character has completely wiffed a locked-on soul arrow shot when I had a clear line of sight on flat geometry to an enemy.  No objects in between myself and the enemy, no weird positioning.  I was within range to target.  Target locked on.  Character inexplicably aims 45 degrees to the right and fires at a wall.   I think it might have something to do with the targeting bias for non-targeted shots (no lock on set).  Sometimes I have noticed my character will aim for barrels if I just fire off a shot at random in an area with no enemies around.  The game might have a conflict between non-lock on bias and locked on shots, with the non-lock bias winning out even when lock-on is set.  
 
This never happened in Demon's Souls, even when I was hanging half off a staircase trying to hit a guy stuck in the geometry of a wagon.  Never a problem.  This is new.  It needs patching.  :/

Might just be a problem specific to Soul Arrow though, since it has homing capabilities now. I really don't know, though.

Yeah, that's what I'm thinking.  I tested a little bit with the crossbow just now and no such issue came up.  Only Soul Arrow so far. 

i really hope its not a big problem as the aiming was one of the few things i was really hoping theyd fix.

soul arrow does not hom
homing soul arrow does though

soul arrow does not hom homing soul arrow does though

The shot will curve but you have to be locked on to the enemy for it to work.  Homing soul arrow's behavior is a different piece of business.   
 
I don't think it's the curvature of the shot causing the problem though.  My character firing in a different direction entirely than the enemy I have targeted is the issue.  Like I said, 45 degrees or more to the side.  It's hard to replicate.  Most often occurs on the first shot towards a given enemy.  Subsequent shots fire and hit correctly. 

I wouldn't say it homes it exactly cause you can easily miss, but it definitely follows the target (much more so than soul arrow in Demon's Souls).
I noticed the exact same thing today when I was playing.  You're right, I would be locked on with my character facing the locked on target (like normal) but when I go to use the spell my character pretty much just fires it into the floor. Specifically I seem to have noticed it does this after I had previously been locked on to another target, killed it, then the game auto locked me on to a new target. My next shot at the new target is a bust.  It doesnt do this every time, maybe 3 times over 3 hours of playing today, so I definitely think it is a glitch.