It's been possible to complete content and pull your weight in dungeons on a bow/bow build. The unfortunate part of that is bow/bow builds are just thought of as inferior so even if you can pull 40k+ solo you still may be kicked from PUGs.
Bow/Bow is viable (even in Endgame, if you are not pushing for scores on leaderboards of the new trials). The damage is relatively similar to the ranged magicka builds, but you have a little less survability and it is more difficult to pull good numbers in a trial environment because you depend of some cast-time skills.
That being said, somewhere in this forum I saw a Bow/Bow build (i dont have the link right now), you can look for it and adapt it to your particular playstyle.
Currently i'm having lots of fun with my bow/bow bosmer, i just (almost) cleared vCloudrest+0 last night with my guild (we are progressing), and i have cleared vAS+1, vMoL, and vCraglorn HM trials with it.
I'm not using crushing weapon, i use snipe and here's a little 3 mill parse where i got 41.5k (i usually get between 40k and 42.5k depending on RNG), the sustain is just fine in solo and almost perfect in an organized group.
My current build is:
- 5 Briarhearth (nirn bow with poison enchant)
- 5 Relequen (non-perfect), because RELE OP (with VO instead, -which is non-optimal, there are better options- i got 37k)
- 2 Stormfist
- 1 Malestrom bow (nirnhorned)
Using max health and max stam blue food.
In a raid environtment you can swap some of the fighters guild skills for defensive skills if needed (i recommend bone shiled on backbar because when it is combined with the psijic shield and the CP small shield while blocking you get a 12k damage shield, which is enough to survive most of the hardest scenarios in a trial environment).
Hope this can help you and encourage you to try it, it is VERY fun and rewarding for us that always wanted a pure bow build.