I think Toady has talked about Revenants before, and how giving them specific tasks and goals -because revenants exist because they want something - was something he'd have to look at.
As for zombies, I think if they were toned down and still came in their giant hoardes, thatd'd be fine. You don't even have to mnake them strong, their whole schtick is that they are slow, stupid, falling apart, and there are more of them than you have bullets/bolts/arrows/bodies for. They are attrition made flesh, so to speak. Albeit the flesh is falling onto the floor in maggot-eaten chunks.
I haven't actually seen that post but that sounds like an interesting idea.
To be fair though, that sounds a bit like it'd be more quest material in the sense that you could help the revenant achieve their goal to put them to rest, instead of being the target of "there's a undead monster somewhere in the jungles of clenching; it's big, deadly, and totally awesome, GO KILL IT" type quests. So I'm not sure if that helps a lot with balancing zombies, it'd feel like kind of a waste to give revenants the current zombies physical attributes only for them to be easily skippable.
To be honest, I didn't make the exact distinction at first as the only types of revenants I'm familiar with are the ones from Warcraft and Mortal Kombat, neither of which are the "classic" depiction of being undead with a purpose.
As for regular zombies, I do agree they should come in large numbers (despite the lag, but I suppose that is inevitable - oh God I said it), that's a basic principle of zombies, they just shouldn't be AS strong as they are now, maybe only slightly stronger than a generic human/elf/dwarf/goblin so they wouldn't be entirely useless against armored adventurers, but also not having the power of a jackhammer in each limb.