I'm really liking this thread, lots of discussion. I found this in the FAQ as the answer to "How does Slaanesh earn DACs?":
A: Slaanesh earns one dial advancement counter each
time he places two or more corruption tokens in the
same region as a Noble or Hero token during the
Corruption Step of the Corruption Phase. The dial
advancement condition printed on the Slaanesh Power
Sheet is incorrect.
Now, the thing that I see that leads me to believe Slaanesh could earn more than one token per corruption phase is "each time..." So if there are two regions with nobles, and as Slaanesh I place (I dunno) 2 tokens in one and 5 in the other, then I get two DACs, one for each region as I satisfied the requirement. I think the "or more" is with respect to the number of counters placed in the specific region as opposed to the overall number of counters placed in a corruption phase. If I were to place 1 token in each of those regions I just talked about, then I would not score any DACs despite my overall placement of 2 corruption tokens as they were placed at separate "times". In my games we play the same way with Tzeentch and Slaanesh as we do Khorne and Nurgle, despite the noted difference.
Further down in the FAQ we get this:
Q: Does placing two corruption tokens
in a region with one magic symbol and
one warpstone token fulfil Tzeentch’s
dial advancement condition?
A: Yes. To earn one dial advancement counter, Tzeentch
must place two or more corruption tokens in a region
with a minimum of two magic symbols, two warpstone
tokens, or at least one of each – one magic symbol and
one warpstone token.
Again, it says "to earn one DAC...", which I read as "each time this happens, Tzeentch gets one." I do agree that clarification would settle this no problem, but in the mean time I'm just gonna stick to what I believe to be the implied rule.