I can help you out with this.
I packed out a sheep over 20 km with the cabelas pack. The strap broke about 4 km from my truck - it was kinda my fault cause I was pretty tired and just grabbed one strap and hoisted it up. That pack is all right but won't stand up to what you want
Fell for the marketing bs and got a dragonfly
pack. This is more of a day hunt bag and is hardly big enough to use for back packing multiple days. The rifle holder works well but you might hit the crown of your rifle when going down hill and it's a joke to put it in there when the bag is loaded. I practiced hiking with 70lbs in it and it's not too bad but not too great either for a comfortable ride. You won't get as much in it as on your tatonka and I don't think the zip in panel would hold up for too long. If you plan to use the extra gear hauler bag or whatever they call it you need to buy extra straps to go around it as the ones they provide are too short and they failed to mention that. I still have mine for a day trip gear bag but in my opinion it's not what they hype it up to be.
Next I went to a mystery ranch 6000 and can say that this is in my opinion the best you can get. Practiced hiking with the same load and it is night and day difference in comfort and you can strap everything in tight to your back so it rides better. If you load up the erblestock to 6000 cubic inches it's gonna be hanging way back. I can't say for sure but I would bet that their external frame load hauler would be great for what you want
I have also used the badlands 4500 with the same practice load. It definitely rides better than the erblestock but the 4500 capacity is from extending the part with the drawcord that is usually under the top cover all the way above your head. Not the way to pack weight.
Hopefully this helps you out and you only buy one bag. Go for a mystery ranch. Hands down the winner. I pack my rifle in the water bottle holder on the bottom with the sling around my neck and bought some extra water bottle pouches for the waist belt