The Traveler has to have some kind of time technology of his own, or the Guardians would be wiped out. Their continued existence proves this. Yes, the Vault Hunters have shields, but that have no other technology augmenting their physical capabilities (or mental, in the case of a Warlock). Without the presence of the Traveler and Light tech, Hive tech may well indeed be able to drain everything from a vault hunter. Remember, the earth was completely dead save for a few hive minds in deep orbit or buried under the ground, and then the Traveler had the ghosts resurrect the humans capable of welding the light. Nothing in Borderlands shows probability for resistance to the forces the Guardians fight against constantly.