I Agree the shoulder strap needs to conform to ones shoulder, from where it starts to make contact with ones back all the way to the armpit.
I disagree with the statement that the strap has to be sewn on at an angle to match the top of the shoulder. The shaping of the strap and the angle at which it comes off the pack (wether or not is is sewn on at 90deg or not) will determine if the strap lays properly on the body.
One of your examples, the osprey mutant, has a yoke attaching the straps to the back panel of the pack. The yoke is sewn on at fairly close to 90deg to the pack, the yoke then angles outward giving proper fit over the shoulders. I did own a mutant 38. The trouble with using a yoke attachment is then you also need to employ load lifter straps to keep the pack snug against the upper part of your back. I don't feel load lifter straps are necessary in a properly fit and loaded pack with weights under 35lbs.
The same thing ( and proper fit ) CAN be accomplished with properly shaped shoulder straps sewn on to a pack at 90deg to the pack body yet angled out in a V-shape. This will help keep the load snug against the back and eliminate the need for extra pieces. AND if the strap is shaped properly, it will match the shape of ones shoulder and be comfortable.
I have worn many many packs, not being able to find the idea pack for me caused to to start making my own. Shoulder strap fit is the first thing I notice when I put on a pack. I have made over 40 variations of shoulder straps, slowly refining the shape and the fit. I will also add that I prefer to not use a hipbelt with loads under 20lbs. Carrying all the weight on the shoulders lets you know pretty quickly if the fit is right or not.
I have seen some great packs made recently on this forum, I would say the people making these packs know as soon as they load them up and try them on wether or not the pack fits.
TO the pack makers out there. Keep up the great work, you know what works for you. It is either comfortable or it isn't. If it isn't, you can change it. Thats the beauty of myog.