I’m personally going with Build 3.
Wiz3 provides future-proof scaling with Quick Cast, and Surespell for Flesh Cannon/future cast time spells. Magic Missiles synergize with JP/HK as well, and the combo is effective even against 80k+ hp monsters.
Linker1 is more than enough, with a JP monster gem you can get 6 links, whereas lvl 10 and 11 JP are both at 8 links.
Sorc1 provides DPS during your spell cooldowns thanks to Summoning (Templeshooter), Servant buffs provide AOE ratio for Flesh Cannon, and additional dark property attack for all your spells.
Necro1 has the 16-hit powerhouse in Flesh Cannon, which would have a total of 10 AOE atk ratio with servant buffs, and gets its cast time reduced/damage buffed by quick cast. Flesh Cannon is probably the 2nd best Mage AOE in the game after Frost Cloud IMO. Shoggoth is basically a slightly better Salamion since he lasts forever, is a decent tank and has slight bit of AOE similar to Templeshooter. Flesh Hoop is a ok-ish spell as well. You also get access to Decay debuff to help double your archer friend’s DPS.
Warlock has the infamous Pole of Agony crazy ground deploy AOE every 2mins, Dark Theurge is basically super Flesh Hoop with 25 hits at lvl 5 (and synergizes well with JP/HK due to each hit being single target), and Invocation, which can REALLY go out of hand when AOEing down a large group of enemies, while also providing a damage buff to dark spells.
I’m leveling pretty slowly so I doubt I’ll be reaching R7 anytime soon…in the event that R8 is released, and Necro3 somehow becomes insanely strong (maybe getting Flesh Cannon #2 or even something similar to Frost Cloud etc), then I might drop Warlock in favor of that. If all else fails (aka if Necro3/Warlock2 both end up being disappointing/terrible), I could always take Sorc2 at R8 to complete the Sorc toolset.