hi,
I would like to put here some worst and best units duos:
worst:
sanworm+catapult - useless in defence (catapult only 20 strenght, sanworm is not supported by walls). in attack siege of catapult gives nothing to sanworm.
pegais+red dragon - they give the same bonus (morale) and can be easly kill by 3 eagles
dwarwes + wizards - wizards can't use their main streght (movement) because dwarwes slow them down, also bad to defend city.
kraken/see serpent + non flyer - well...
best:
(grand) archon + devil - very strong and negates all bonuses
green dragon + wizards - very fast and wizards protect dragon from eagles
elephant + heavy cavalry - deadly on open (heavy cavalry = 25 + 10 + 12 = 47)
wofls + elves - great on forest , against flyers, and some ambush, also fast.