Synergies
Synergies should work with the opponent too. For instance, you bring Wolverine to fight Cyclops NXS, both attacker and defender get the +90 crit damage.
Only the champ that has the synergy gets the buff, so for example GR VS Blade, GR gets the benefit from matching up with Blade, but Blade doesn't get any plus.
Makes paring fights even more interesting and complex, and creates the possibility for debuff synergies.