Offense mods giving more critical damage than CD mods

I guess you haven't tweaked much with offense.

See Josh_K post about damage formula in this thread of 2016:
https://forums.galaxy-of-heroes.starwars.ea.com/discussion/66818/ig-88-critical-bug-video

You can test it yourself. Go enter a node with a rebel with no leadership and note down the damage done to the enemies. Then enter again but with Wedge leading that toon. Note down the damage done.
Remember there's a 5% variance on damage for most chars (ST Han and ST having 10% variance)