"abandon reasonableness" is never necessary; though I think we may be using reasonable somewhat differently. I think "reasonable" includes the idea of "appropriate to the situation"

quoting myself : "There is a supposed "old Chinese saying": The wise man defends himself by never being attacked. Which is excellent, if incomplete, advice. I completed it myself with "But only an idiot counts on not being attacked." Don't use violence unless you really need to, but if you need to don't hold back." http://williambswift.blogspot.com/2009/03/violence.html

As to your overall point, I agree that rationalists should win. General randomness, unknowns, and opposition from other agents prevent consistent victories in the real world. But if you are not winning more than losing you definitely are not being rational.