Jumping on a little late here, but here goes...

Collect your kit (including food and water), then decide how much capacity you need. If you think you need four panniers, then reconsider several times whether you need all of the stuff you are taking. The reason I say this is that once you've convinced yourself that you must have four panniers you preclude a real game changer: the ability to get by with a saddle bag, frame bag, and handlebar bag - a la http://carouseldesignworks.com/.

If you plan on doing a great deal of single track on your Fargo, you might find that panniers - regardless of design - get in the way. If it's only occasional single track, then a "high rider" front rack mounted pannier is eminently doable. The problem, of course, is both brush and the "walls" formed on both sides of the trail due to traffic.

I am primarily comfort rather than weight driven, so I have reluctantly concluded (multiple times) that I need more carrying capacity than afforded with the "bike packing" set up epitomized by Carosel Designs (et al). But as others have posted, I also eschew the multi pocketed and hence heavy Alkel GT series in favor of the less featured Arkel T series, which has finally been acknowledged here as not much heavier than their Ortleib and Jand "equivalents".

I use a pair of T-42's in the rear and a modified pair of T42's also in the front. I do the latter because I find "front" panniers to be too small to be useful. When mounted high, there is no problem of scuffing on the turns with a Tara on a 700c wheel and certainly no problems with a Swing on a 29er.

The Arkel product is indeed robust. I have toured over 25k miles and they are only slightly faded (black). The internal frame and plastic stabilizer indeed add weight, but if you carry a couple of days worth of food and a couple of gallons of water they're nice features to have. Yes, I would agree that if you don't plan intercontinental touring over many years, you can function perfectly well with a cheaper brand. OTOH, there is a market for used premium equipment and I have little doubt that I could resell my panniers now for half of what I paid for them.

As far as waterproofness goes, I'm firmly in the breatheable-is-better camp. Firstly, because I use pannier covers anyway to shield my panniers from the cow poo that is ubiquitous on BLM land and to light myself up while on asphalt. (Anybody with access to a sewing machine can make pannier covers: appropriate and cheap materials in head-turning colors are readily available.) Secondly, when it's sunny the panniers often heat up enough to drive off the moisture of most anything packed in the panniers.