So - did we ever get any clarification from Gen Con... Did players get to take a defense test [of some sort] against grenades and indirect LOS (A) spells?
Yes we did: there's no defense test against grenades, indirect LOS (A) spells, and other "zones of damage." The defense against these attacks is to take precautions against them. This is really really really true, and been confirmed by multiple sources inside the company. So unless there's been a meeting somewhere to which I wasn't privy, you really really honestly and truly don't get to make a defense test against grenades or indirect LOS (A) spells.
Very well. Then can we please get an explanation as to how counterspelling is meant to be used against area spells? The text goes out of its way to describe how you can give the bonus to multiple people, but counterspelling only adds to defense tests, and area spells like Fireball have no such tests.
Spell defense dice are rolled against Indirect Combat spells the same way they're rolled against other spells with no defense test: you roll them as a dice pool of their own.
So, let's assume the Mage rolls against incoming Fireball. What happens in each scenario?
A) Mage rolls Counterspell. He rolls 5 and enemy rolls 3 on Spellcasting. Mage wins with 2 net hits. Fireball dissapears, Mage is immune to Fireball or Mage's Counterspelling causes the Fireball to scatter?
B) Mage rolls Counterspell. He rolls 4 and enemy rolls 5 on Spellcasting. Mage loses with 1 net hit. Mage's hits are wasted? Does he reduces the "net htis of the grenade test" with his own hits? You know, the "The test is like that for grenades (p. 181): a Spellcasting + Magic [Force] (3) Test with scatter of 2D6 meters." on page 283, Core.
C) Mage rolls Counterspell. He rolls 3 and enemy rolls 3 on Spellcasting. What happens with the tie?
I'm kinda torn by this one. Which is why I kinda hate this Aaron guy, sometimes his answers make no sense whatsoever.
We've already decided that the line in the book about "-2 to dodging explosions" is just supposed to be ignored, b/c there is no defense test to modify. Well by that logic, Counterspell shouldn't apply to a Fireball at all, b/c it's just another modifier to a non-existent defense test.
* If you do allow it to apply, then logically it makes you into Fireball repellant. So long as you can reduce the caster's net hits under the Threshold 3, the Fireball will scatter. According to Aaron, since there is no defense test, you're allowed to roll just your Counterspell skill. Which means you do not get to roll Reaction + Intuition + Counterspell... you only get to roll your Counterspell rating.
A) Assuming that for whatever reason, they rolled Spellcasting + Magic [Force] and only got 3 hits... while you only rolled Counterspell and got 5 hits (statistically meaning you've got Counterspell 15)... since they didn't get their Threshold 3, the Fireball would scatter.
B) Again, assuming you've got Counterspell 12 to mathematically score 4 hits... since the caster didn't get his Threshold 3, the Fireball will still scatter.
C) Once again, assuming you've got Counterspell 9 and they suck at rolling their full dice pool... the caster still didn't beat Threshold 3, so it scatters.
If you're allowed to use Counterspell for AOE spells, the only way it's going to land on target is if the caster overcomes your check in addition to the Threshold 3. Which really shouldn't be too difficult realistically. They're rolling Magic 6 + Spellcasting 6 + Combat spec 2 = 14 dice averaging 5 hits. You've only got Counterspell 6 averaging 2 hits, giving them just enough to meet the Threshold.
** But... the easier answer would be to say that Counterspell doesn't apply to Fireballs, for the same reason we don't worry about the -2 to defense against AOE. You can use it to avoid a Flamethrower or Lightning Bolt, but AOE is just targeting a point in space that you happen to be near.