I don't usually have Scarlett in the front lines, mostly because I took Hyperopia. I also didn't say the skill wasn't useful, it's just situationally so. Much earlier, you can get somewhat of a similar effect by using Splintered Arrow on a single target too.
I also wasn't trying to suggest that Marksmanship wasn't good. It's just that like many abilities in this game, the special arrows are pretty situational as well, and unless you have someone crafting arrows constantly, you would need to keep buying them or hoard them for the "I could really use this now" situations that rarely actually come.
On a side note, I've had somewhat of a drought of good spells (this in turn causes my Ranger to do most of the group's damage). I know you can craft whatever now, but almost all of the spells I've been able to craft that I don't have are level 15 Master spells, and I'm only level 12. I think level 9 was the last level either of my casters got anything new that was interesting, and I haven't found a single damage dealing spell for Jahan from his starter stuff other than Headvice. It's pathetic. He mostly just
and occasionally uses crowd control when it's ever needed and then wands.