Stun - As mentioned earlier this will be your most used dark arts set and should be one of the first you attempt to finish. Aim for recast reduction>magic acc:
Iaso hands can get augmented with 3-4 haste, Iaso legs can get 4.
In legion replace pensee with:
Veneficium ring is probably not much better than Maquette ring given the only cast an occ quickens spell cast proc would matter would be a stun if you didn't have alacrity up. It does happen you run out of stratagems though, so your choice if its worth the extra inventory slot.
Hedera cotehardie is a slight improvement if you have the invnetory room and are not capping gear haste from gear/outside sources like atmacites. Other easier to attain swaps include rubeus legs, rubeus hands (only with legs), shantotto legs w/ haste augment, Repartie gloves>magavan gloves.
The reason af2+2 hat and af1 shoes are not listed is because you should almost always have alacrity up while stunning (which annuls their bonus). If you use spellcast and have the inventory both are slight improvements with alacrity down.