...what?
Void is mandatory all the time. If even one player gets an aegis, void instantly deals more damage than deathcap- for much less cost.
All the mana from RoA is only useful for the Seraph shield and AP, neither of which is enough to justify the purchase. You'll already have more mana than you need by far. Plus, RoA isn't universally strong the way it currently is next patch- only 80 AP isn't that attractive. The health also isn't that ideal on Orianna. I'd rather get the higher damage and slow from Rylai, the CDR from Zhonya/Abyssal, or the resistances from Zhonya/Abyssal.
PLus, Abyssal is actually stronger late game and much weaker early game now. Before, Abyssal was a great rush because it instantly gave you 20 magic reduction. This increased waveclear, made it hard for people to 100-0 you, AND let you 100-0 your opponent. However, as soon as your opponent saw you building it, they'd have to build it too. And once they built it, they'd have the MR to not be 100-0'ed. Plus, as soon as someone gets an aegis, abyssal is instantly no longer worth it. So Abyssal actually made you weaker, but it was still required.
Now, it gives more MR and more late-game MR redux. It's more targeted at defense when built early, and provides more of that even in the late game. 5 MR reduction will deal much more damage in late game than 10 AP, and 10% CDR is thrown in as a kicker.
