Long live Paweł "The Not Fool At All" Feszczuk.
Great stuff you started here, thank you. I finally beat it with fully all around army BUT with insanely armored Goblins returning damages.
Dead end battles "catapults vs catapults without ammunition [with eventually with goblins]" shall be fixed in some goal average way.
I'd say upgrades need balance, but with statistics you may find some relevant tweaks. For example, I don't see a world in which you can build upon "pin" + "crits against on pinned units". Too low % of pin with only a 1s pin, units attacking usually less than 1 per second... the mix of % and seconds appears really odd. And you need to sacrifice more "immediatly decisive" upgrades to build upon higher % of pin and then find the %crit against pinned... naaah.
Have a good development, sir.