Similar to valkyries without the UP bonus, their ability is to fly for a short duration while aoe in a small radius.
Really niche imo, because its a duelist really.
you can check the details in the dmm sit...kappa.
bow archers are basically the melee version of archers. I used an event plat version to cover my lack of archers in dmm till i got spica.
I won't suggest wasting resources on leveling a silver one though. Your core should consist of gold and above to start off with and dmm is quite generous with their drops. You should obtain spica there twice as fast, since they have 2 days of DC dailys (thur/fri) instead of thurs only.
The new plat pirate is has the same abilites as bashira, triple shot. Great for those new players who lack range dps. Her AW is similar to spica which makes her highly valuable if you have other good pirates/sailors.