Pretty big, but the Aflatoxin and the Arsenic being only one in such a big deck gives them pretty low chance to appear.
What's the Mark of Time for, anyways? If you're going mono, use your mark accordingly.
I'd recommend using something like this:
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52g 52g 52g 52g 52g 52g 52g 52g 52g 52g 52h 52h 52h 52h 52h 52h 52o 52o 52o 52o 52o 52o 52q 52q 52t 52t 52t 52t 52t 52t 8pk