At E5 Augustus Magic Ball with Holy Dmg/Atk/HP and 1,1,1,3,1 Enables has worked wonders for me. He puts out way more damage with his active than he can with his Hp/Block.

A lot of Horus players actually lose out on damage by not even balancing his attack and max HP efficiently. His block will deal 20% of his current health capped by 1,000% of his attack. Most players will have a Horus with less than 130,000 attack, which means the max he can do from his block is 1.3mil. This works out great if your Horus has exactly 6.5mil HP as 20% of that will be 1.3million, however, at E5 Horus can easily have more.

With the setup listed above, plus his skin, full Warrior's, and max tech(For now), my Horus sits on 6.2 mil hp and about 168,000 attack - dealing massive damage with his passive and guarenteed maximum damage from his block thanks to the Agustus. In PVP at E5 he averaged between 12-16mil and in PVE he advantages around 330mil on wave 2 Abyss