Like goofy4tink already said, there are no pre-set groupings of resorts, no pre-set routes, no pre-set order of drop-offs. It's a fluid situation at all times. Just because you were on a bus with Resorts A, B & C one time, that's not "the usual" way ... there is no usual way. They know about how many people are going to which resorts at about what times, so they constantly change it to make it the most efficient.
In fact, the last time I was there (last month), they made a grouping right off the tops of their heads, just to clear everyone out of there.
But some groupings can be more common than others. The resorts are broken down into 4 geographic zones (and no, there is no "HS" zone). Here are the zones and the resorts in them (I'm leaving out the associated DVC resorts since they should be obvious, such as BoardWalk Villas ... should be obvious it's the same as BoardWalk Inn, etc.):
MK - Grand Floridian, Polynesian, Contemporary, Wilderness Lodge
EC - Yacht Club, Beach Club, BoardWalk, Caribbean Beach Resort
DD - Old Key West, Saratoga Springs Resort, both Port Orleans resorts, Fort Wilderness Resort & Campground.
AK - Animal Kingdom Lodge, Coronado Springs Resort, Pop Century, all three All Star resorts, Art of Animation
[I think that's all of them]
Here are the rules: If a DME bus has resorts from only one zone, there's a maximum of 4 resorts on the bus. If the DME bus has resorts from one or more zones, there's a maximum of 3 resorts on the bus (to make up for the extra driving time).
The dispatchers tell the driver which resorts are on the bus, but the driver decides the order. So with no pre-set groupings and no pre-set order of drop-offs, you can see why you can't definitely know what your DME experience will be.
The only exception is Polynesian and Grand Floridian. If they are on the same bus, the bus MUST stop at POly before Grand Floridian for logistical reasons ... they're on a dead end street, and if the bus goes to GF first it would then have to make a left into Poly, and that left turn is too small/tight for a big motorcoach, it would never make it without having to stop and back up and try again, so they don't allow it.
So as for my most recent DME experience, last month, it fit the mold in that there were 3 resorts on the vehicle (a small van) and we crossed 2 zones ... we dropped off 1 person at Port Orleans French Quarter, then my family of 4 at Contemporary, and then there was a family of 3 heading to Grand Floridian.