There should be certain types of bows that can be crafted for use with sharpshooter/arcane archer. Don't know the name off the top of my head but you should be able to get the increased range on them. Quivers/Arrows will not bring it closer to what a Ranger can achieve as they also have access to the same Quivers/arrows + all their talents/passives that buff being a ranged bow user. I think rangers get something like +50% damage just to their LMB attacks alone. Will it do acceptable damage? That depends on what you consider acceptable damage I guess. Can it be "ok"?, probably. Competitive?, no.
You can take talents that improve the toxin damage but its nothing noticeable. Toxins mostly exist to modify what Diffusion does. Crafted toxins increase your toxin proc chance, not toxin damage. This is all toxins currently do. All the classes and abilities have not been touched in years. I would expect everything to get an upgrade at some point before release.
Shameless plug. https://winterblades.net/crowfall-calculator
Capping multiple stats was possible in the last version of the game when we had end game top end gear and training. I would think it will be possible again but not until we reach that point again.
I would do Dregs for sure when they come out if you have people to play with. There is more to do there. God's Reach and Infected are really just leveling/training zones.
Limited imports will not really effect your builds all that much. Good gear will be crafted gear and that has a much higher durability. It is just not currently possible to craft good gear yet on live. Getting mats/crafting is mostly gated behind passive training. If you are in a guild that does harvesting/crafting, it really should not matter.