Yeah, it wasn't that difficult once I worked out how to set it up. I used the table below of Sword vs Armour damages with an index function based on the numbers in the row/column headings. Here's an example:

=INDEX($E$2:$H$5,RIGHT(O$14),RIGHT($A22))

E2:H5 is the Swords vs Armour table.

O14 is the s1 part of the a4|s1 column label.

A22 is the a2 part of the a2|s4 row label.

Thus, this works out the mitigated attack value of Sword 1 vs Armour 2. This table as a whole worked out the mitigated attacks for columns versus rows. A second table worked out rows vs columns, and the table shown above merely compared the two values.

I agree though, the strategy is complex and I think perhaps in these situations always comes down to how risky/analytical you think the other players going to be, and how you think they think they're going to judge everyone else. And... well, how do you even start doing that? Especially since, most of the time, people will just... stop behaving rationally when faced with this kind of situation.