From my experience in pnp, cover is indeed useless... In the mid-game/endgame, as you fight enemies armed with guns that have such high armor penetration values that cover is not enough. Against low-tier mooks, cover is fine (beware of flamers though as these bypass cover, flamers are always useful). Instead, I realized it's better to stack up your armor points and especially toughness bonuses so that you can shrug off bullets (or hide behind someone with such scores). Cover adds armor points so having bulky power armors helps with hiding behind cover, funnily enough. If the bad guys are melee-based though, cover is useless and they likely do enough damage to kill tanks, so you better take them out first.