Origins Rogue Archer Build

I will preface this by saying that archer is probably my least favorite style in DAO... but the most recent run I did in this game was an "all archer" party and I solo'd an archer rogue.

1. Bard is the best archer specialization, then two next best are Ranger or Duelist depending on if you like pets or not.  I go Duelist then Bard mostly.  You can use "Dueling" even with bows, so that is a nice big free attack bonus early game.  Assassin is mostly a backstab oriented spec, and you can't backstab with a bow.  If you do take it then you probably only want Mark of Death.

2. This is controversial, so the answer is really "it depends on what you want."  Basically on a rogue if you have minimum in str to equip the armor you want and all other attributes go into dex or cun you will be fine.  The controversial part is which actually does more damage, although old threads will say cunning.  Overall late game min-maxed cunning build does a little more on target damage most of the time, the exception would be against targets with relatively low armor but high defense.  Min-maxed dex character will have higher attack and higher defense.  In a party game, I don't find that any rogue needs huge defense.  For a solo you want mostly dex.  My solo archer ended up with defense just in the 140s IIRC, as I started investing in pure cunning late game and Suppressing Fire is great.

3. Depends.  Shale is the best archer buddy most likely, but mages w/ buffs and debuffs can help.  Alternatively, taking Leliana and Zevran (as bard) can give you three Songs of Courage, which do indeed stack.  There is a wiki article about archery strategy and max crit chance.  Of course the old Alistair + 2 mages  + you setup works.

4. Dalish.  Not just story but also because the loot and available items are better for it.

edit: some more thoughts.

The thing with archery is that many of the actives are not very good in terms of cost - benefit.  And some of the sustains aren't necessarily great either.

Best stuff is Suppressing Fire, Scatter Shot and then Master Archer passive.

Other actives:  Pinning Shot is relatively useful early game, but it is in the worst archery line.  Shattering Shot is most useful for knockdown, the potentially huge armor debuff usually isn't needed, especially not on a cunning archer.  Crippling Shot is not good, and Critical Shot isn't really an auto-crit (it crits if it is a hit, which is no good for Misdirection Hex).

Arrow of Slaying can generate a big number, but has a bug and really the cooldown and stamina aren't worth it.

Sustains: Suppressing Fire stacks with each hit, which means you can apply pretty large attack debuffs to targets if you have some rapid aim.  It is probably like about 15 points of defense or so.  Also note that Scatter Shot will apply it twice to each target it hits if Suppressing Fire is active.

Rapid Shot is decent early game when you have low crit chance, but no sources of rapid aim.

Defensive Fire is very situational.  You get a very large defense bonus potentially, but aim speed is really low and so your dps is tanked (unless you have Repeater Gloves on).  The nice thing is that with +30 defense you can become unhittable a lot earlier than anybody else in the game (easiest solo v Uldred I did) but as stated DPS will be poor w/o Repeaters.

Aim's problem is that it isn't entirely intuitive as to when it will add DPS.  Very early the flat damage buff and attack buff may barely make up for the aim penalty, but I would just run Rapid Shot.  Later the aim speed kills it unless you can get in the ballpark of -1.6s total rapid aim, which basically requires either Shale or Repeater gloves.  If you don't have one or the other just leave it off.