I’d recommend just switching to a Meteor Shower build like Lexa suggested. It’s exactly the same playstyle as your current build, just stronger.
But if you want to stick with Manald Heal, here’s some changes you could consider:
First off, get a new Deathwish and Etched Sigil like Lexa suggested.
Second, Lightning skills that come off of Etched Sigil procs won’t trigger Manald Heal. So I’d ditch Blizzard: Lightning Storm and Energy Twister: Storm Chaser. Swap to Black Hole: Supermassive for a pull to bring stuff together for you to channel into and Magic Weapon: Deflection for toughness.
Right now you are using Blood Bracers but you don’t have any shields! So swap in Magic Weapon: Deflection as I suggested above and also drop Astral Presence for Galvanizing Ward for another shield to synergized with your Blood Bracers. This will make a massive difference for your survivability.
If you find you don’t have enough Arcane Power after dropping Astral Presence, pick up Arcane Power on Crit on your source. You might not need this if you drop Aether Walker though, as Hergbrash’s belt should have you covered for arcane power.
I would just straight up get a different amulet, but even with that one, roll the lightning damage to crit damage. Manald Heal is bugged and doesn’t benefit from lightning % on gear, so you are much better off with crit damage. Lightning % will still buff your lightning meteors, but crit damage will buff both skills, so crit damage will be better for you. You need both crit chance and crit damage on every amulet. You can just roll your current one for now, but be on the lookout for a Squirt’s Necklace with int/crit chance/crit damage socket. Your shields from Magic Weapon: Deflection and Galvanizing Ward with Blood Bracers will keep the damage bonus up. It’ll be a big damage boost for you.
If you find you still need more damage, consider picking up some attack speed. More attack speed = more Manald Heal procs. A very easy way to do this would be to swap Aether Walker to Echoing Fury in the cube. Echoing Fury gives you a big boost to attack speed when you kill stuff. Then you can run Illusionist like you mentioned.
If you find an ancient pair of Nilfur’s boots, you could wear those, which will free up your cube slot for something different. Dunno what you’d put in there really, could do Ice Climbers + Stone Gauntlets, but it’ll be hard to find a good ancient pair of Stone Gauntlets if you don’t have a barb or sader. Note that Ice Climbers nullify the Stone Guantlets attack speed and movement speed debuff, so it’s a nice pair of items to get some free toughness. Could just do Nemesis Bracers too.
And if you can survive without it, I would drop Esoteric Alteration for Bane of the Trapped.
Then obviously try to get ancient versions of your non-ancient items.
Something like this: https://www.d3planner.com/935102254