After some days of thought, here’s how I see it:
I don’t think that thaumaturgic spells based on conflicts are something like a 26-shift attack. The “based on conflict” notion is about determining the complexity, not the rules per se. I’d like to demonstrate my thought with an example (based on the one I used in my game):
A Warlock tries to inflict a mental extreme consequence (WORKS FOR THE RCV AND DOESN’T EVEN KNOW IT) on his victim (a chemist who produces drug for the mafia; the RCV want him to spy). The Victim has a Discipline of +2 and a Conviction of +1, so the spell needs 17 shifts of complexity to work (+2 Discipline, +4 maximum dice roll, 3 Shifts of stress and 8 shifts for the extreme consequence). Now if this was a simple attack (as per the rules of attacking), two strange things would occur:
1. The victim would actually have to roll his Discipline. So the Victim would most likely (because he probably wouldn’t really roll a +4) take another consequence, instead of only the extreme consequence. Or to put it in another way: to create an extreme consequence actually needs less than 17 shifts of power (probably only about 13).
2. If this would be just an attack, like described under Conflicts, the victim were to choose the consequences. He could choose to take a severe and a mild consequence instead of an extreme. He could even choose the wording of the aspect that comes with these consequences, instead of taking the aspect the warlock wants.
But in my opinion, those 2 “occurrences” are false. That’s not how I read the rules. I think this is not how the rules are intended.
This brings me to another example on the question if the spell works at all, if the complexity is not high enough. Let’s consider a tracking spell. Would you say that if the complexity is, say, 2 too low (8 shifts would be needed, but I come only up with 6 during my ritual), the spell would partially work (maybe something like “the person we seek is somewhere in this block), or would it simply not work?
To use my other example from above: Would the victim have to take a severe consequence, instead of an extreme consequence, if he sits behind a ward with a strength of 2? Or would the spell fail?
This is where I'm still unsure. I think I can recall something about Victor Sell’s spell cast on Harry during Storm Front, but I don’t have my book at the moment, so I cannot check.
Thing is, if the heart-exploding spell would work even if it has to be cast beyond a ward, without taking the ward into account when determining the complexity, it is so really, really hard to protect against such a spell at all. It would need a ward with a strength of about 36. But such wards would be virtually indestructible. The rules tell me that a ward with a strength of 8 is pretty high, and it is: it needs 16 shifts to destroy it (to bring it to a strength of +0). So wards are pretty useless against strong thaumaturgy, or they are pretty indestructible using anything else short of thaumaturgy. The scaling is odd, in my eyes.
Opinions?