None of the weapon packs are really necessary (for that matter, none of the DLC is really since you can play the DLC heists if you join a room of someone who has it, it's just that you can't yourself choose it from the heist list). I like the Assault pack though. The shotgun one is kind of situational, but I like the Raven and M1014 from it (the former because it's a good primary with ample ammo, and the latter because it's a giant help when loaded with HE rounds since it has a large ammo pool even when reduced). The sniper rifle one can be a godsend too, but you don't need more than 1 person with a sniper on any heist, and the Thanatos only has 18 rounds to begin with since it's so freakishly powerful.
Overall though I'd say the Hotline Miami weapons are the best by a good bit. The briefcase, while horrible damage, is hysterical to use and has a extremely large knockdown chance. And the SMGs with it are all quite good, the notable winner probably being the Tech 9.
