Best use for this is for status bolts/arrows, where you're not worried so much about damage but more about the bolt landing at all and inflicting the desired effect. It's a good piece to have around for a completionist/soloing THF or RNG, but I wouldn't put it too high on the priority list.
Rangers beware. You will lose 25 ratt for for the +20 racc. Most Rangers slot in amemets +1 for the +15 ratt. So, but filling it with this, u lose a huge chunk of ratt from amemet, then another -10 from this cape.
This piece is great for Rangers, but even better for Corsairs. Since Corsair only has a "B" (skill 250) in Marksmanship any extra racc helps. If you TP build with a Joyeuse and dont wanna lose -10att you can always use your Amemet/Amemet+1 and macro this in for your Slug Shots/ranged attacks.
With the -RAtk especially, you're going to have to make up RAtk in other slots. Guess what? Those slots can also be used for RAcc. Save yourself the 150 ABCs, stick with Amemet +1, and put the RAcc. elsewhere. This cape isn't worth it.