I love Surly, but that does not include their overweight racks. Go for a Tubus Cargo rear rack and one of their front racks. They are stiffer than anything else I know, and they last. Th eonly snag is that they are epoxy coated, and this will scratch, and then start to rust. Being the obsessive type I am I had mine chrome plated.
Which is where the Cosmo comes in - stainless steel so absolutely no rust (unlike chrome which can rust). The side rails add to the weight but IME beiing able to mount the panniers lower does help handling.
I don't think decent aluminium rear racks fail very often and when they do it not likely to be catastrophic and probably bodgable till you get a replacement. If You're on a budget I wouldn't compromise on the front rack and get something like the Tor Tec Expedition for the back.
Ah the voice of someon who has never had a rack fail on them.
A rear rack failing would probably fall within most people's definition of 'catastrophic' - one minute you're riding along and all is well and the next minute you're stuffed. You might ne able to bodge something if the rack failed in the right place but otherwise I'd be doubtful.
The rear rack is the one that carries most of the load so I would say it's the last place to compromise. I wouldn't compromise on the front rack either though. There are lots of other bits of equipment that aren't 'mission-critical' wher you can save money.