In search of the perfect sleeve.

Do you need sleeve cap ease?

I'm not sure. What are your thoughts?

I made a jacket at the end of last year and had a real problem setting in the sleeves. Most patterns seam to have a huge amount of sleeve cap ease. I've never really got to grips with it. 

When working with curved seams you always have some ease, do you really need extra ease?

I get the whole argument about fitting a flat piece of fabric to a curved part of your body, but I've taken apart quite a few RTW garments that fit well and very few have ease, and if they do it's minimal. So what is the deal with home sewing patterns that they have rather a lot of ease? 

Does anyone have any answers, even better does anyone have a drafting tute for the perfect set in sleeve? Or will I be forever drafting dropped shoulder designs or swearing over frustrated attempts to set in a massive amount of ease?