Need help modding GAC defence teams in the future!

You seem to be under the (wrong) assumption that all characters on defense need to have mods with defensive stats. That's incorrect. Attackers still benefit from offensive stats, key characters that need to possibly out speed your opponent still benefit from speed, characters that have abilities that trigger from crit chance still benefit from CC etc. even when on defense.

If you want more specific advice please post a link to your roster.