Just a short post about the said items.
All the pages about monster banners say they give you a "minor" buff against the enemies in question. Now, how many of you think +50% (+100% in expert) damage and +25%(+50% in expert) damage reduction is "minor"?
USE THE BANNERS, you won't regret it. Makes invasions a lot easier. Active editors, what do you say? Should that "minor" be upgraded to "Major"?
(source , and of course everyone can test it)