Okay, as a flavour thing, I don't feel evocation is appropriate because that school creates matter or energy out of nowhere, where as the flavour for this spell is supposed to be that you are calling something to this location from another.
Part of the reason is that it's Paladin 2 is because I wanted it to phase in as flying creatures became common, but before reliable methods of player flight are affordable. I could perhaps see it going up to cleric 4, as they do have other blasts
And as a personal choice, I do like scaling rather than fixed damage, as I feel it provides a nice sense of progression and it keeps spells somewhat relevant throughout progression of the game.
SR: No would make sense, as it does require a to-hit, and a large part of the targets of Clerics and Paladins (Outsiders of opposed alignment) are going to have decent SR. ...that and it targets the thrower, not the person the bolts are thrown at, hrrm, good catch!