I run a 3 2* setup, with my low-star half deck being Nightmare, rather often. I find that it does just fine, because two of the 3*s I will pull in that situation are Phyllis and Artus -- a great card with solid damage that goes through DR, and a great DR.
According to the auto-calculate function in the Public Presets plus a little bit of terrible math skills from grade 1, chances of getting four 2* for a 5/5/5/2/2/2/2/2 deck is approximately 7.14% and the chances of getting three 2* and one 5* will be 42.86%
Correct me if I'm wrong, been ages since I did math.
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