All good calls
I'd support all of those changes, and I like the Shadow Orb banked idea for buffing Mind Sear
With that said, our Shadow Orb system does need to be made more robust - we have 1 non-execute Orb Generator, and 1 finisher - that's a pretty barebones system that screams to be fleshed out. One of the most obvious finishers they could add would be an AoE finisher.
I suspect the reason they didn't do it was because our level 90 talents are kind of AoE finishers already - so they felt it might be too good or something - but certainly after MoP we've seen Shadow is in no risk of being too good - so maybe WoD will bring it about
Maybe an ideal solution would be both a 5% per orb stacking Mind Sear buff, and also an AoE finisher - so you want to stack up orbs for searing, and then when the mobs start getting low - you want to burst them with the finisher (before they start dying off and your finisher hits fewer targets). That would require both preparatory awareness to bank orbs before the AoE phase - and also active awareness to anticipate the damage of your finisher within the remaining healthpool of the lowest mobs in the pack
That gives us lots to think about during AOE - sounds fun