Questions about archery

The thing is though, longbow proficiency isn't really 'free' with an Elf, since the alternative is going with a human and getting a feat that you can spend on whatever you want. In my view, the necessary feats for an archer are point blank shot (because it is required for other stuff) and precise shot (because it allows you to fire into melee). Rapid shot is nice for an extra shot per round, but can wait until you can absorb the to-hit penalty, and is less useful than sneak attack dice and a source of invisibility. I generally go pure rogue, with a level of fighter in there somewhere to give me longbow proficiency when I'm about to buy a masterwork composite longbow and a belt of giant strength (and I rarely fail to have a pang of regret somewhere that my level 13 character is 'missing' his 7th D6 of sneak attack because of it). In my opinion, aside from spellcasting, sneak attack is the most useful ability in the game, and just as I'm reluctant to delay my acquisition of the next spell level for my casters by multiclassing, I really don't like delaying my rogue's sneak attack progression. For me, Precise shot, as many dice of sneak attack as can be fitted into the build (no reason why this can't be 10D6 at level 20) and a reliable source of haste and improved invisibility spells are the core of a successful archer build in this game. Other than earlier access to things like improved critical, I don't really see what levels of Fighter or Ranger add.

 

Fighter and Ranger levels add BAB, and Fighter can get you weapon specialization and other useful feats like Quick Draw. Ranger levels are also how I keep Survival, Spot and Listen as high as possible.

 

Don't forget to add "speed" to your bow when enchanting it for the extra attack per round. Your crafter just needs to know the spell haste.

Also, I too tend to keep my rogue purely rogue for the extra d6 and the crippling strike at 10th level.

A level 10 rogue sporting a crafted compound long bow of strength with improved invissability cast on her can be a true terror.

 

Assuming 20 levels, one wants to have 19 levels in rogue for 10d6 sneak attack damage, 4 special rogue feats (Crippling Strike, Improved Evasion, maybe Slippery Mind and Defensive Roll or just new, normal feats), lot of skill points (Tumble, UMD, Disable device, Open lock, maybe Search, Spot, Listen, Move Silently and Hide, but Invisibility is easy to get) and 1 level in high BAB class with martial weapon and shield proficiency - fighter (free feat), barbarian (faster movement, more skill points, maybe rage) or ranger (favored enemy, save throws, most skill points) - or 16 levels in rogue (8d6 sneak and 3 special abilities) with 4 fighter levels for weapon specialization and one more attack (due to higher BAB, 16 instead of 15). Currently my both rogues are 14, so I will soon check both options.
I wonder if Keen enchantment (and possibly Improved Critical) always adds 2 to threat range? It makes bow critical from 20/x3 to 18-20/x3 (so not double, but triple range in that case). If we can't spare a feat for Improved Critical, this one is nice option (costs only 1 ability point), with Seeking (1 point) and maybe Speed (3 points). Probably +5 enhancement +Speed +Holy, or +5 enhancement +Keen/Seeking +Holy +Burst (Shocking) are best picks. Seeking is quite nice, dealing with concealment. Speed is convenient, but 3 points is a lot, so it's better to use Boots of Speed or have someone else cast Haste.
About feats - Improved Precise Shot is very good, but doesn't ignore concealment (=20%, at least not Blur casted from cloak). Deadly Precision is superb for ranged rogues.

 

Looks like Keen enchantment works like intended (double weapon's critical threat range), it just description that is wrong (showing 18-20 instead of 19-20), here I rolled 18: