Even before the latest balance changes the best weapon configuration for a black mage was spiral staff + blank scroll, and as long as Titan's Grasp is in the game none of the one handed weapons are likely to be meta relevant since you can (and should, if we're being optimal) spend a comfy training vacation as a temporary warrior to equip a two handed weapon + black scroll.
Izkanti Dress has always been worse than Tiran Vestments/Habit.
Helm is either Crown of Winter or Circlet of Clarity depending on whether you value the Dawnbreak + defenses of the crown or the crit on the circlet more.
Geomancer's Bracers, Weedwalkers, Ouroboros Pendant, Cloak of the Deeps are all still either BiS or in the conversation for it (there's an argument to be made about the sunder immunity from the seaweave shaman cloak being more useful than what the Deeps gives you but I think either way it's close regardless)
For the belt I think Fertile Girdle is going to be best most of the time, 10 initiative on one piece is really hard to pass up when the only (spellcasting) offensive opportunity cost you're paying is an anemic 5 spellpower on a sallow belt. As soon as you leave glass cannon territory a Senninbari or Champion's Belt start making sense as alternatives.
For rings the single best one is the Ring of Pale Flame. For your other one it's either Guldring or Ring of Fortune, again depending on how you value 5 spellpower vs 5 crit (5 fire damage is pretty negligible). Since both are additive, and assuming you're wearing everything above so you have much more of the one than the other, this decision is therefore between a ~2.5% increase to spellpower and a ~12.5% increase to crit. I personally go for the crit here, but if for some reason you have Presence investment, or are a Valkyrie and care about the Aurora of Vigor effect, or care about leadership etc Guldring makes sense.