I define it as robust in that as the market changes through time, the region will more or less continue to outperform.  The primary assumption here is that the market price action characteristics will remain similar through time.

A region has to be a grouping of squares or it is not a region.  If you're looking at a single green square in a sea of red, you're looking at a system which happened to catch a single large price movement at the perfect time - which the neighboring cells did not catch.  By choosing this square, you would be "cherry-picking" a combination based upon a single trade which will never occur again.

You're looking for a profitable system which captures the general characteristics of the market.  Specific enough to give direction; vague enough to avoid curve-fitting.