How much damage the spell does is known to the AI via the XML. When you play, don't use select items and spells based on what they say they'll do? That's what the AI does.
Well, that's kind of what I do. But as a casual gamer, say, maybe I'm retarded because it's difficult for me to tell how much damage a spell is going to do *cough* UI improvement *cough*
I know from experience that a certain spell tends to rock-ass. But the description says something like "8 damage +4 per fire shard"
How many fire shards do I have? I don't remember, at least 1 or 2, or maybe 3? Can't remember. And then I have +50%, and another +50%, and maybe another +50%? I just take the "+50%" whenever it comes up as an option on level up. So, does this mean that if I have 2 fireshards and 3 of the +50% traits that it does some amount of calculation of damage, but is the +50% stackable? I, as a player, don't have a straightforward way of seeing/knowing this.
(8+4+4)*1.5^3 ? (=54) or
(8+4+4) + (8+4+4)*0.5*3 ??? (=40)
What would be handy would be when one mouses over a spell in tactical combat that the little window that pops up would say "base damage 54" and possibly a calculation there to show you how it's calculated, and when you click on it and point my little spell wand cursor over the dude that I'm thinking about nuking it would say "37 fire damage" or something, again possibly with a calculation to see why it's reduced from 54 to 37 based upon the dude's resistance or whathaveyou.
Again, maybe I'm retarded and this is how things currently are, and I just haven't noticed or something. And maybe I'm lazy for not looking deeper into the back-end of the operation to figure these things out without dumby alerts popping up and just telling me the answer. But most players are more intellectually curious about how to take over the world, than figuring out if their flaming dart is going to do enough damage to the MOB left with 23 hp to finish him/her off, or leave him/her with 2 hp.