One of the things to remember about fly fishing, many of the knots are unnecessarily difficult and serve mainly to separate fly fishermen from worm drowners. I will fish everyday from June 7 into late September up in Bristol Bay. We will fish everything from Grayling to Kings on fly rods, Most of my knots I learned bait fishing. When I am at the lodge, with my readers and nailknot tool, I'll replace a butt section to fly line with a nail knot. In the field I simply use a uni knot. Never had it fail, tied properly. It is very rare to replace the butt section however.
Same scenario tippet to leader, at the lodge I'll build my leaders with blood knots; in the field a uni knot or surgeons knot. Uni is very fast, clean and strong. Most importantly I can tie it almost with out looking, important in bear country. Kiss principle, but I rarely, almost never fish tippet lighter than 4x. Too many big fish around.