No u dont. Guardians are stuck at the same level as the enemy. Always even in low level story mission. Enemies however can be higher level than you. Before house of wolves, we were stuck at 32 while hard mode crota was level 33. So we did less damage becuase we were a level below. Now we are on the same level as crota so we do more damage. Thats why it only takes 1-2 swords to kill him. The only bonus u get for being 34 is the higher armor stats. Thats all. As for atheon and black hammer is concerned . 365 weapons do more damage than 300. But the big difference you are noticing is that when someone is using perk for defender titan i think its call illuminated. The benefits of weapons and blessing of light are further increased. So tht difference is probably when someone has that perk versus someone tht using that perk.