4000% FB, 400% Grand Vizier, 600% Nilfurs, 325% Deathwish, 150% Etched Sigil = 41x5x7x4.25x2.5 = 15,247% multiplier
4500% Arachyr, 150% Chiroptera, 100% Chiroptera (ATS), 300% RoE, 300% Bakuli, 30% Sacret Harvester, 25% Mantle of Channeling = 46x2.5x2x4x4x1.3x1.25 = 5,980% multiplier
both builds can possibly get max AD, CoE, Endless Walk, Taeguk, PE, Trapped = same additional multipliers.
So this builds multipliers are 2.55 times stronger than Firebat Arachyr (15,247 / 5,980 = 2.55 )
Meteor vs. Firebat needs to be tested which skill is more efficient in clearing density. Wiz got way more additive Dmg (Spellsteal) however missing out on a passive like Gruesome Feast.
Dmg output for Wiz is due to the gameplay mechanic decreased (overall probably ~half dmg) since you need to alternate casting Meteors and keep Channeling while selfcast Meteors burst down. So you won't get full benefit from AD and won't cast Meteors on a constant speed. Additionally you obviously deal close to no damage while you self cast Meteors. Depending on PE stacks you can dish out 2-3 Meteors before losing Taeguk. Needs to be tested further. But obviously making that 2.55 bigger multiplier alot less impressive than at first glance.
Dropping Taeguk for Bane of the Powerful might be an option here to optimize self Meteor casts and starting the Channel when Meteors fall down. After all in Groups and with Spellsteal there is plenty of additive Dmg already available...
This build can selfsustain Arcane Power with Hergbrashs. With Globes (Reapers Wraps) maybe Witching Hour is an option.
In the end I really see no reason why this build shouldn't keep up or even beat Firebat Arachyr.