Hey Johnny,
The way that the hair rig works, is that the heavy weight drives the hook into the fish's mouth when they take off. Usually a "hook set" is not really needed, just a slow sweeping motion would be good enough to drive it deep into their mouth.
With the setup we're using (feeder packed with method mix and sometimes 1-4oz weight), we need the heavier line to cast these rigs. Of course it depends where you're fishing, but if I'm fishing at a swim where bigger fish are common (15-25lb average), I'd prefer using heavier lines just to avoid losing the fish as well. It's kind of like, you can also use 6lb test to fish for muskie but most won't do that.
As far as the mono vs braid, I might be wrong but it seems that the zebra mussels cuts up mono pretty easily. People use 50-80lb PP for their hooklink up at the St.Lawrence.