Well...
Light is using Sancs. There's little doubt about it. Sancs cancel poison and stop Nightmare. Plus Light probably has a Miracle or two. Basically, what I'm saying is that we can't win until we drop a Fractalled Dragon.
How about we cut out the Poisons and use 2x Dragon with 2x Fractal?
Something like this, maybe.
6 Dims, 2 Plagues, 2 Dragons, 2 Fractals, 1-2 Arsenics, 16-17 Pillars/Pends.
I'm out of town and can't test, but this might end up being our best option.