Been wondering because I'm not a vet player
Tried Arrow Rain for Bow but smh idk how to control it :/
Also wondering why Lightning Slash for Twin Swords sometimes attacks by either charging straight ahead (like Lunge Step) or like a short version of Blue Fang Blade

Imo, Arrow rain is more for bosses, and a great tool for it at that.

Rapid shot series is best bow skills.

And I hate every twin sword skill except for the two ougi identical to the sword ones.

for i only use rapid shot 1 till now (lol) decent damage,fast cooldown,and it follows the enemy as long you lock them
for twin sword lunge step is quite decent
well i am still new to this so..

I personally enjoy using icicle arrow, which is a small AoE skill, and I especially love using it for boss fight. Rapid Shot is good for spamming.

As for twin sword, I always enjoy the twin sword lunge skill, since it's a ~10m distance closer, and twin slash for beginner skill. Other than that, any elemental skill that does a wide frontal AoE skill is handy to have when you are getting mob.

Lightning slash is a ~5m elemental closer, which is really the same range as the the sword melee range, but at least it's better than the 3m range of the twin sword.