I think that even if you're not working to failure, you are still stimulating a muscle sufficiently enough for it to grow. So that to me qualifies as a working set. I don't care for constantly working to failure anyhow. It has it's place and time, but I don't think you need it every set, every workout to achieve your goal. There are many schools of thought on this subject.
Dorian feels that you should get blood in the muscle, then hit that nail hard as possible and that's that. Charles Poiliquin feels that you need a few sets, and for a specific period to keep sending your muscles/body that signal to adapt and grow. Pavel Tsaoulintewhateverthefuc khisnameis feels the volume should be low and NEVER to failure.
All methods work.
I feel that overall, you need all these methods, only how you put them together is your make or break piece of the puzzle.