The character in question has the Farm, Hippy Store, and Nuns finished as a frat, the junkyard finished as a hippy, and finished the war via wossname. I'm pretty sure that means I finished the arena and lighthouse as a Hippy, but I can't guarantee that.
With +25% combats, I saw 79 lobsterfrogmen in 200 adventures. Using the normal approximation, apparently that gives me a confidence interval of 0.395 +/- 0.068? (so base rate of 0.145 +/- 0.068). I'll run more adventures if needed.
(long story short: I'm definitely not seeing a lower combat rate. If anything, I'm seeing a potentially higher rate. Also, I don't really know statistics.)