While I am no expert, here is how I usually dealt with this situation.

You are right, those numbers are not intended for wandering monster encounters. You wouldn't roll for a random encounter, then roll 30d10 to see how many orcs were there. Even with a mid level party, that would be a bit much all at once. Rather, those numbers were more intended for when putting together a dungeon or small one-session campaign. You'd say "I want this to involve orcs and worgs" then roll to see how many there were. 297 orcs and perhaps 59 worgs, for example. Then roll treasure for the group.

There's going to be some sort of home base for the group - perhaps a cave or warcamp, depending on why they are there or what they are doing. The most important creature would have the most important gear, so the orc chief would have the +1 longsword and the +2 chainmail. Maybe a +1 harness on the lead worg, as well. Other important enemies would have other important gear, perhaps including a shaman or similar if there is magic items in the stash. (Although not necessarily - the orc chief might just have the scrolls and no way to use them.) The rest of the group has standard treasure - coins and the like - out of the stash, then whatever is left is the chief's hoard. It means that killing individual orcs and worgs isn't worthless, just that the majority of the treasure is in the main base. Where players would expect it to be.

Quote Originally Posted by Yora View Post
Here I am a bit uncertain what the original intention might have been. It seems like parties traveling in the wilderness might randomly come across lairs. But there appears to be no mention anywhere on when to make a wilderness encounter Wandering Monsters or a Lair. Entirely possible that it's left completely up to the GM to roll a wandering group or a lair, but I'm still curious for what the assumed practice would have been.
Wilderness travel is a bit different from dungeon travel, although I've not really used the rules for such. Dungeons involved a closed box with corridors and limited access to other rooms. In general, if there's 100 orcs in a dungeon, you're probably going to be fighting through 100 orcs (or close to it) to get through the dungeon. Perhaps you find a circular route to bypass some of them, but it's pretty likely that a party will run into the orcs there.

In a wilderness, though, players have a large area they can move around in. They're free to fully retreat after the first encounter with a scouting group if they don't want to mess with orcs. They can simply get up and leave the area, and unless the orcs feel like pursuing en masse (or are just moving that direction) then the encounter is over. Moving around the orc group might take some time, but it's entirely possible to get to the end of the wilderness trek by avoiding the problem orcs entirely. This is mostly why the wilderness encounter is so much larger than the dungeon one: it is a large camp or even a functional town, while the dungeon encounter is closer to a bandit camp hiding in a cave.

Plus, I'll note that the presence of non-combatants means that the encounter might not even be a dangerous one. Just because they're an orc war party doesn't mean they're going to object to an adventuring party selling a +1 weapon for something the orcs have available, either information or non-useful magic items.