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I can see why they tweaked abilities upwards to make them more competitive, but that's only from the damage standpoint. A lot of the abilities that get high use have far superior mechanics, and I don't think twisting around some numbers is really going to get me to switch my play style around. They really needed to hit the cooldown, cost and mechanics of many of the low-use abilities in order to make them worthwhile, which based on the preview they did not do.

I am not sure that you have modeled the damage calculations correctly. Think of it this way, if you have 100 dps before crit/dmg modifiers, 100% crit and 50% crit damage, the xbow bonus takes you from 150dps to 200 dps whereas the bow bonus takes you from 150 to 172.5. At 100 dps, 50% crit and 50% crit damage, the xbow takes you from 125 dps to 150 dps whereas the bow takes you from 125 to 143.5. Similarly, at 0% crit, you go from 100dps to 100dps with the xbow and from 100 dps to 115 dps with the bow bonus.

From these examples, we can see that crit% does indeed have an impact on the viability of bows vs xbows. The issue in your calculations is that you are multiplying non-crits by the crit damage modifier.

It should be more along the lines of:
1.15(baseDPS)(1 + critChance * critDmg) = (baseDPS)(1 + (critChance)(critDmg + .5))
1.15 + 1.15(critChance * critDmg) = 1 + .5critChance + critChance*critDmge
.15 + .15(critChance*critDmg) = .5critChance

So your break-even depends on your existing crit chance and crit damage modifier. Also, the crit chance you have is a bit harder to model due to sharpshooter.

Personally, I look for +10 disc, +dex, +crit, >14% IAS. Without all these attributes, I would not take a second look at the quiver. A socket is also nice to have, but if it has all 4 other attributes then the quiver would still be a must have.