One school of thought in this is about the bike trail, so low trail bikes handle front loads better while high trail bikes handle rear loads better. For example I'd load a Surly LHT 40/60 front rear. The ogre is a mountain bike though so I have no idea about that. I'd suppose it's a high trail bike so more rear bias should be the better choice.

If you're going to be doing a lot of singletrack, then perhaps racks aren't the right choice, especially if you are going to load them heavily. Racks are attached with relatively small screws, which is completely fine for roads, or even dirt, but going actually MTB'ing is going to stress those screws a lot. You do see off road tourers using racks quite often, but those usually hold the bulky light stuff such as sleeping bag etc. and the heavier stuff is in frame bags and/or backpack