As for hit rate, it isn't an issue for an adequately buffed cunning based archer by mid game (Heroic Offense, Rally, etc.) It gets even better (read 100%) with Shale and/or multiple bards.
As for damage advantage, in addition to AP and critical %, the CUNN rogue also gets +2 base damage for every 10 Cunning with Tainted Blade.
I forgot about Tainted Blade. That's because I only got a lot of the DLC recently.
The point about Heroic Offense, Rally is part of what I was trying to get at with synergies. There are a lot of ways squadmates can buff your attack or nerf enemy defense, but there isn't so much that buffs crit chance, and only a couple things that work like AP (sunders).
I loaded up my recent rogue and used the respec mod potion on her to try and get a feel for the numbers, since it has been a while since I played a dedicated cunning archer and apparently deleted that character.
Level 21 dalish rogue
Far Song, HoH (Long Sight for buff), Red Jenny's, Felon's, Bard's, Spellward, Lifegiver, KttC, Andruil's.
-This was a solo dagger rogue (dex of course originally) and I didn't bother to find or console in all the ranged gear which would improve it slightly. This also avoids DLC gear like High Regard and Sorrows. It would be better to buff with max cunning gear when turning on SoC. Also this is with a second stack of SoC from Lel. Zev could potentially give another if you build him for it.
Str 24
Dex 44
Will 31
Mag 20
Cun 77
Con 28
Def 99
Atk 137
Dmg 63.1
Crit Chance 52%
AP 23
Far Song itself gives 10 attack, 10 from Dueling, some amount from SoC's. Every other hit should be a crit this way with +25% crit damage bonus (Far Song + Red Jenny's).
The stat distribution came from a couple of factors. Respec mod just pulls all points out which messes with racial distro, and fade bonuses. So first I set the attributes to the same thing I had at character creation. Then I put in the fade essence / font points, then put a few points in Str and Dex that would meet prereqs.
It is possible to meet bow prereqs with slightly lower Dex, but you can't get Arrow of Slaying without 30 "real" dex. For a true auto-crit build you can actually skip that if you want. Also possible to save a couple points out of Str if you plan to have a bunch of strength gear laying around to boost stats to put on other things.
In any case, I like cunning archer a bit more for teams, and of course dex for solo in Origins*. Don't think either is useless; both work, just in different ways.
*As before, in Awakening Dex is a lot better because of Accuracy, but you can respec there if you want.