These are some builds assuming you want a +1 crit mult in one way or another and the option for slayer arrow when running in FOTW.
I gave up on Paladin 15/Art 4/Fig 1 when I found out the AP don't work for getting slayer arrow, int to damage, and endless fusilade at the same time (although 14 paladin/6 artificer could use them at the same time thru insightful damage).
I think 5 rogue (10 RP, 30 doubleshot with killer, 10% alacrity) > artificer (rune arm and fusilade)/ranger (sniper shot) so these are the builds that incorporate that.
Also fletching stacks with returning ammunition so you don't need conjure bolts. In my tests I got 33 full volleys (3 bolts plus doubleshot) off with 10 bolts. In practice 100 bolts lasts thru multiple quests so when you stack 1000 75% returning bolts you can wait long periods before rebuying ammunition.