You are a NUKER first, tank second

We skip aghs in this build because you want to go in, do as much damage as possible, get out, and repeat. This is why after Shroud and Shiva's we go for Heart of Tarrasque as our 6th slot item, you will be just as tanky and once you regen up enough outside the fight you can jump back straight in. You cant do this with Aghanim's Scepter, not to mention Nullifier or even Eul's disabling your Reactive Armor barrier in an instant