I came from class build A2>R3>Sc>X
I really feel R3 sucks in iTOS:
Steady Aim : it just gives you +10% damage (40% up time)
Bounce Shot : Its not that bad but its also not that good skill. It is just so-so and you can live without it.
Spiral Arrow : This is really strong burst, but due to cooldown issues (36/43 with attributes on) I don’t know if its really worth to take this for 2 circles
So I was thinking what to replace my R3 with different 2 ranks, and I have thought of this build:
A2 > Ra > Sc > Ro > Fal > Cannoneer
Synergies:
Feint + Barrage
Double Flare Shot (Using Capture)
Capture + Skills from allies
Circling + Multi-Shot = OP
Circling + Cannon Blast/Cannon Shot/Shootdown = will hit more than 5
Circling + Skills from allies
On top of these are:
Swift Step : +25% Crit Rate
Steady Aim : +10% Damage (+100 Flat Damage)
Sneak Hit : +75% Crit Chance (from behind)
Build: PURE STR
PROS:
Decent AoE
Maybe has chance to do better on ET (since you have Falconeer support)
So many synergy to choose
Decent on PvP (I think? since you have Scout)
CONS:
Lacking of single target - mainly Critical Shot will be the filler 
PvE : AoE Oriented
PvP : Decent
WB : As long as your rotation is correct, then you MIGHT have a chance (but of course Fletcher3 will own this spot)
Comments are welcome.