I'm concerned with Caster Attack rolls for two reasons -
1) Doesn't the need to make "to-hit" rolls regularly require the +X implements? I don't think the "+3 holy symbol" thing sounded very popular, especially with those 4e-leery.
2) I may be wrong, but I worry that, while my players might like being able to roll dice to cast spells, they would miss being able to roll dice to resist spells. "I know you have a good Fort defense, but I rolled a 19, so you die." And as a DM who wants to have fun too, I don't care for the "players roll all the dice" suggestion.
I've discussed this very concern with my group:
1) This problem is mirrored on the melee side as well. Needing a +4 sword to effectively hit a monster's AC is just as problematic as needing a +4 staff to hit a monster's Reflex with your lightning bolt. The solution is not assuming +X to hit weapons/implements in the game math.
To me, the '+3 Holy Symbol' is no more odd-sounding than the '+3 Battle Axe', as I dislike plussed magic items in general. However I think most players would agree that finding a 'Holy Symbol of Luminous Radiance' is just as exciting as finding a 'Flametongue Longsword'.
2) Not all magic spells would use an attack roll to see if they hit. Makign a saving is more fun and probably even more realistic for certain types of magic and effects. Both should exist, and which one is used should be dependent on the nature of the attack being made.
For magical attacks that resemble weapon attacks, things like lightning bolts and acid arrow, the monster making an attack roll to hit a defense makes more sense. Rays, bolts, missiles and other magical projectiles, and touch spells, should all require attack rolls.
Less 'aimed', indirect spells like hold person, confusion, stinking clouds and power words should require the target to make a saving throw.
An example of both mechanics coming into play would be something like magical rays that carry an additional effect or condition i they hit the target – such as disintegrate and Finger of Death. The caster, PC or NPC, should make an attack roll against the target's Reflex defense to hit initially and do damage. The target then should make a save (perhaps Fortitude) to resist the effect and avoid being instantly disintegrated or slain.
-Wulfgar76