+spell damage and instant spells

[savaughn]

I'd like to know how good the rules of thumb are.
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Actually, I you were dead to rights the first time, at least as far as every piece of +damage gear I've ever used or tested on my mage, warlock, druid, etc.

This is actually one of the most consistent pieces of WoW. There's some interesting logic behind how +damage is applied to channeled spells, DoT's/HoT's, and stuff like Moonfire and Immolate where there's an initial damage hit followed by a DoT. The general rule is that the entire amount gets applied, generally subdivided by the individual damage ticks. That said, I think there's still a few spells out there that are bugged in this regard.

You had this question earlier:

People who know better than me say that spell ranks which are learned below lvl 20 get a sharply reduced benefit from +Dam/+Heal. Spell ranks learned above lvl 20 are said to always gain the full effect.

So, this is actually a misunderstanding. Lets take shadowbolt as an example. Shadowbolt has a 3s cast, meaning it gets 3/3.5 or 86% of your +damage gear. As other folks have mentioned, this does not change if you have Bane reducing the casting time to 2.5s. The base timer is all that counts.

Now, when +damage gear was first looked at, people noticed that Rank 3 Shadowbolt does not get the 86% of the bonus damage. Rank 3 only gets 80%. Similarly, Rank 2 only gets 63%. This has nothing to do with the rank of the spell. This is because Rank 3 is a 2.8s cast and Rank 2 is a 2.2s cast. There's no weird hand coded diminishing returns, it's just a different casting time. Every spell that gets a longer casting time at higher levels (fireball, frostbolt, etc.) has this.

One other comment. I have not tested AoE outside of mages with +damage, but for Arcane Explosion at least, I have not seen any kind of "we assume 3 targets" thing. By my math, it's been a straight 43%. My AE hits for around 300 per hit and I have no where near the +327 damage gear that would be required if there were a 1/3 in there. I haven't really ever tested this for, say, Hellfire or Hurricane, though, so this may be an exception.