The issue is that Aquilla’s is THE chest piece of choice for Invoker’s set. Sure, you’ll regen wrath quickly enough with the high attack speed innate to Invokers, but losing that damage protection is an instant death sentence in high GRs. What’s more, it only affects on-cast Bombardment, not Belt of the Trove bombardment.
You also would NOT take any other rune except Barrel of Spikes. As Invoker’s is a pure-Physical build, this means we take +%physical damage wherever possible, and the only other non-physical rune for Bombardment is Impactful, which is just terrible. Minefield is also terrible. As Invoker’s does not stack neither Critical Strike nor Critical Damage, Annihilate is terrible. Finally, Targeted is superfluous, since the spread for Bombardment still 100% ensures that it will always hit a target, and generally will hit the nearest target to you, providing the target itself doesn’t move (And if it’s a fast moving target, Targeted is even more likely to miss since it aims at where the target WAS). Swapping to any other rune means you lose out on 40-60% damage, and Bombardment no longer benefits from the Physical burst window
In terms of RG/Elites, Invokers is one of the best builds in the game at killing elites, but only in solo play, and only when you gather enough mobs to keep your invoker stacks at 25 (look up density gathering in D3).
Finally, LoN-Bombardment would STILL be the better build for a player looking to have their damage based heavily around Bombardment. This change would only help to infinitely boost Invoker’s AoE capability, which would probably boost us straight to GR 150, since we have near-0 AoE capability atm, and are 100% a dedicated elite/GR slayer build (Even Impale build has AoE capability with Area Damage, we lack even that)
Keep in mind that the D3 devs tend to significantly overbuff, and then overnerf builds, they have shown themselves to be 100% incapable of balance in this game.
If you want Bombardment playstyle, seriously, give LoN Bombardment a try via the Legacy of Dreams gem. It’s very solid.