DOUBLE SHOT AND ARROW BLOW

First of all master only one skill! Choose between the two. All in all
this skills is fairly equal. it's a matter of deciding which do you
like most (I know if I say that, it doesn't help much in deciding,
lol). So just to say this, no matter what you choose between the two,
you'll end up fine! It doesn't mean when choose AB you can train in
Golems, DS can still too... so don't get stuck deciding what to choose.

I wont give you too much math stuff or about damage calculations but to
me Double Shot has more stable damage than Arrow Blow. This is VERY
important to us Bowman since we have an unstable damage with our
regular attack. Both arrows can have a Critical Shot skills so damage
goes up form time to time. The 2 mp Consumption is not that big problem
since the ratio between Arrow Blow and DS is 8:1 (means if you
constantly fire DS evey 8 shots AB can do 9 shots). on the other hand
since this skill fires 2 arrow (130% each) you'll be draining alot of
arrows bolts at the start.

AB is one powerful shot pure 260% attack plus Critical Shot! at Some
people like this skill because if you happen to dealt a certain damage
to enemies, the enemy gets knock back (enemy flinch)then you can fire
more! because DS has half half damage per Arrow you'll have a hard time
flinching enemies until your high leveled.

Although the damage is fairly equal example your AB can fire 1000
Damage and DS can fire 500 and another 500.

DS gets more chance of critical shot and AB goes with max damage if you
got critical shot. DS can still knockback monsters once you get to higher
level (45ish i can knockback Wraiths)

Example: the monster Golem can only be knockback at a certain damage
around 1k+ AB can deal 1k+ damage, DS can deal 1k+ but the damage is
delt from 2 arrows. To make enemy flinch the damage must be done from
one source only so this means AB can make your enemy flinch if you got
a damage 1k up. on the plus side for DS since DS usually get a Stable
Damage if you spam DS the Golem easily dies.

Also if you choose to have Final Attack when you reach Crossbowman
class then both of this skill can have extra Damage. if you have DS
then you can knock back enemy by Final Attack since its has 250% damage
if max.

In the end its almost same... but if you still can't decide go with
Double Shot, im using it and im having no problem with it. In my opinion
this skill fits perfectly well also if you think about it, it has more
MP consumption so its probably stronger.
http://www.gamefaqs.com/computer/doswin/file/924697/39297