I don't know if they'd done this before anytime recently (since the Rhapsodies were introduced), but yeesh.
This appears to be far more than "Double". I know it is anecdotal evidence, but I've done 4-5 recipes now across 3 different characters, and watched a family member do one as well, and all of these recipes were Lv80+.
Before this, a Kitron Macaron without Ionis gave rather slow skillups post-80. Usually, it was 1 skillup every 5-10 synths, sometimes worse.
After this started, the skillups are almost every single synth, with 5-8 synth gaps of no skill randomly thrown in. I got my Woodworker from 94 to 100 in about 75-80 synths, I got my Goldsmith ~1.5 on about 20 synths, family member got .6 bone out of 8-10 synths, and my blacksmith got over a level out of 4-5 stacks of adamantite ore, making ingots.
This was all using Kitron Macarons without Ionis.
Just posting this, for anybody who still needs later level crafting stuff.... this "Double" Skill Gains seems to be more than double, or something is stacking to produce far better results than they let on, lol.
So, the whole point of this... do your skilling now! (or the last week of Jan if you don't have any materials)
Edited, Jan 1st 2017 6:09pm by Lyrailis