Once I make a demo map for this tutorial I'm going to check out if there are any more possibilities when you make the dummy face a hidden unit, maybe we can still get 360 degree rotations working smoothly, don't count on it though.
Rawr, I did these tests..
SetUnitLookAt only updates approximately every 0.2 seconds..
So its like dusk's choppy knockback system
(and also you can't do pitch properly with this (unless you can somehow do negative fly heights at runtime?))
edit: it also takes a long time to get the dummy unit set to proper spot -> need to put on edge of map if you want projectile dummies not to glitch
edit2: attached testmap (tx,ty on setdummyfacing should be simplified (im overcomplicating by far) ), so you can see the choppyness!
edit3: i probably will still use the way attached in testmap for my own spells, but not have a curving projectile or like that, just to change direction at a chop