Oh, also wanted to address the whole AOE ripple affect. Would this mean that a party could effectively apply immunity/resistance spells to themselves and then target themselves with a weaker AOE spell that is easily absorbed by the immunity in order to prevent others from casting on them? Just pointing out a possible exploit ahead of time.
I'm more for the "the highest current affect of that particular element" is what takes place over the next second or so, superseding all weaker affects of the same element.
Here is my reasoning for this:
If you can overlap all the same elemental damage all at the same time, you could have the case where several players with the same fiery aura that they have made themselves immune to(for example) could run in and decimate another party by running in circles around them as everyone would be taking 5 times the damage except for the immune characters.
If same-element damage DIDN'T overlap, you would only take the "highest damage fire source" currently hurting you and the "highest damage cold source" etc. so in order for players to try to take advantage of this same type of scenario it would be far more difficult for them to provide all the immunities necessary because they would have to overlap several types of damage.
Conditions of particular spells that were not saved against would apply as normal I would assume, so as not to penalize a caster for simply casting the same element of a spell that happened to go off before his. So if in the above example all five fire auras caused a save or be fatigued, despite only the highest aura causing damage to a particular target within range, the target would have to save against every fire aura in range versus being fatigued (or you could apply the same reasoning to conditions, only saving against the strongest one this current second, similar to only the worst bleed affect, etc). This would give players in an FPS environment more of a chance to react to overwhelming odds and yet still be able to throw AOE's, and tactics in this particular environment still apply and would reward proper planning in a party ahead of time.