I'll help a bit pointing the most important point from what Mocchi saying.
It's point #3 and #4:
3. When ranged attack occurs, it's possible to transfer a _fixed_amount_ of enmity
4. The cumulative enmity transfered to other PC has no upper cap. (As such, if you do 1 ranged attack, there will be one occurrence of enmity transfer, and if you do 5 ranged attacks, you'll get 5 occurrences of enmity transfer)
About Sidewinder, he gave an example where Stealth Shot is a better option suppress the enmity from a such very damaging attack. So decoy shot is not the ultimate means to suppress your enmity on the entire fight. The knowledge when to use what is the key to keep enmity at low level.
So, I think this is a pretty good JA overall, you can do 4x as much damage (of 0 enmity level) before you worry about mob have their attention locked on you.
For most of the time, you can stand at max ranged attack distance to avoid boss monster attack. It's particularly hard if you're only given limited space like most of Voidwatch fights or a fight where your tank's back must face the wall.