Slow and Resilient seem to be favored by many on this thread, and I see that as weaknesses that make's me not want to play them.
sIKE, you are debating the benefits of agility over strength, the boxer vs. the wrestler, the skirmisher vs. the heavy infantry.
The problem is there are so many ways to hobble the agile mage. For zombie-based Necromancer, 2 points buys you Enfeeble or Tanglevine. But when Necromancer opens 4 Brutes with Idol then Teleport opponent into them on turn 5, unlike Iron Golems, Brutes hinder escape, follow and attack. With hobbling like Tanglevine, opponent is soon zombie fodder. You mention "Slow" but Lumbering is nowhere near as debilitating as Slow. I grant you Minion's Lumbering and Pest is not good but Brutes can hinder, that's the key difference why I saw danger signs with them.
There is absolutely no finesse in what I propose. Not even a Transfusion free action burst. Just the power of 12 points on 4 Brutes, 16 points on 4 Teleport and 12 points on 6 Tanglevine to flush out your Teleports.
Unless they intend to nerf Teleport so that it can't target enemy mages (I support this), any concentrated creature mass of under-costed high damage/toughness creatures is a threat. Agility can never win against Teleport or Tanglevine. Only more Teleports can. With Slow creatures like Jelly, you have to Transfuse the Jinx Nullify Force Hold, at least it's got some cheesy combo finesse to it. But Lumbering Brutes don't even need that. They follow you and attack when you are not stuck in Tanglevine.
You were perfectly right that Pop-Up Sniper is a huge threat to zombies (and a good play against other books). But all the other solutiions are niche. We are supposed to believe they'll be added into books because they fear zombies? It's not a good sign for the meta when this happens.
I don't think the problem is Brutes. There will always be the next Stone Golem (hit hard in this expansion). The issue is Teleport assassination.