Has anyone managed to find either of these, using DW20's current modpack?
I imagine Deep Hives are rare, but I've spent a lot of time mining 5x5 tunnels at y=±10 and found none.
The wikis all say that Marble Hives are very common - just lying around on the ground, they say. I've done a fair bit of flying around and found 100s of wild bee hives, but not a single Marble Hive.
The wiki information may be outdated...
In MC v1.7 marble hives would spawn on top of grass just like meadows hives, and they would spawn absolutely everywhere.
From my personal experience with MC v1.12, using my own modded instance that includes the mod "Quark," which adds marble, marble hives spawn inside marble nodes. I don't know how they spawn in modpacks where marble doesn't exist.
I have found both deep hives and marble hives in my own modded instance. I don't know about DW20's pack, I don't play DW20's packs.
Deep hives are surrounded by blocks of redstone (yes, *blocks*, not the ore) that spawn up to several blocks away from the hive itself. So they are relatively easy to find, even if they are rare. I've found most by just caving. Sometimes I've also found them because i noticed the bees stinging me, and couldn't locate a rock hive.
The marble hives are more difficult to locate, I've found them by noticing the bees in their general area, when a cave so happens to cross a Quark marble node.
Rock hives always spawn next to an air block, in cave walls and ceilings. But both deep hives and marble hives spawn inside solid stone/marble, unlike any other hive.