In VoG hard you can't revive teammates so your invisibility argument is useless. Invisibility doesn't get you past anything except for the Gorgon's maze which is incredibly easy even without invisibility. Bladedancing will get you killed. Golden gun only helps for taking down praetorians or supplicants effectively but those are easy enough to handle. Golden gun can take down oracles but oracles are really easy to destroy with raid weapons. Titans have bubble which can lock down a vex timegate, offer protection, and either increase shields or damage. Sunsingers are self explanatory and they have fusion grenades which do the same amount of damage as a rocket. Titans and warlocks have more useful supers therefore they are more preferred over a hunter.