Strobo's Bio states that Zodac was assassinated. That, to me, doesn't sound like a battleground death so much as a plot.
Also, just because Photog defeated those two doesn't mean they were killed. They simply could have been drained of their power temporarily.
And as for the Snake Men, it's possible some survived, according to Scooter, as teh spell had a limited range.
(Just my two cents.)