Signed,
Someone who has created multiple +16 weapons using normal EWR and GEWR scrolls since R Grade items were introduced. No HEWR or AEWR scrolls needed. (I'm sure there are lots of us out there. ) :)
I used Giant scrolls all the way from +2 to make my +16 slasher. I didn't enchant all once, just once every few days. The last 3 Giant scrolls took me from +10 to +12, +12 to +15, and +15 to +16. I was hoping for +18, but oh well. I won't complain that I only made +1 on the last giant scroll. :p