For PvP your build is perfectly fine as long as you position yourself accordingly. With musketeer’s high skill damage going dex reinforces both sneakhit’s buff and effectively making musketeer’s skill scale better. As for PvE, you’re lacking a lot in the AOE department. Your 2 AOE skills - multishot and covering fire that which one of them multishot will be needing some AOE attack ratio gears to make up the lack of AOE from your build path. That is not to say it’s necessary but it is indeed useful for helping your team clear mobs as they’d usually be pulled in waves which becomes evermore so apparent in the higher level dungeons.
As for rapid fire, its damage isn’t the best but for PvE it’ll be your opening skill for bosses thus being the only other skill you’d be using at all from QS (along with pavise and caltrops) and so it wouldn’t hurt to level it. Opening with rapid fire debuff then continuing onto your musketeer skills or running shot and then using it as filler in between to reapply debuff whenever running shot is on CD. This is if you’re taking it from a PvE aspect. If you’re more oriented for PvP, level 1 rapid fire is all you need and you can dump the rest into stone shot for a longer stun duration which of course is not 100% either.
As for suggestions, it’s hard to say as I’ve no idea which game mode you prefer. In the end it’s all about how you want to play and what you enjoy. But you should be weary that QS tends hold bosses aggro when you don’t have a tank so it’ll be hard to fully utilize sneak hit. But when you do have a tank, rogue will shine. As for my build i went A2/QS3/SR2