I can't agree or disagree on the weight only because I bought the biggest set of recumbent specific panniers Arkel makes. I will say from what I've seen that Arkel does not over-engineer their products...they simply make well thought out and well made gear. At some point, weight does become part of the price of quality. How much quality is the user's choice. Personally I tend to find and buy the best I can whenever I can. It always pays me back in the long run.

To the OP...you may also want to explore the idea of an "extra-wheel" trailer. This is not the same as a BOB. It literally is an "extra" wheel with its own rack for panniers towed behind your bike. Not sure how well it would work off-road.