First thing I would like to see is that units that are completely in green cover don't get suppressed (as it is supposed to be). Currently, it's simple the roll of a dice wether your squad gets suppressed or not.
It's less a roll of the dice and more that cover bonuses are applied by the entity, but the 'in cover' symbol only indicates the squad. It is either when the squad leader is in cover, or the majority of the entities are in cover, that the symbol appears.
Either way, there's often a high chance there are entities NOT in cover that are eating all the suppression for the whole squad.
Cover is applied by entity and suppression applied to the squad. This is what causes that sense of 'dice rolling'.
Infantry just are too stupid/blind in combat to move or position themselves out of open cover, or simply can't find their way to cover on their own.