Look at all this T-R-A-S-H. Imagine wanting to cube a decent bow at season start, so you can somewhat skip the crappy upgrade hunt that plagues D3 while levelling up.
Over half of them don’t even HAVE a legendary power to begin with, and over half that do ABSOLUTELY SUCK.
Nevermind the fact that their base damage was NOT updated in Loot 2.0 + RoS, resulting in a single Hand Crossbow having much higher DPS than a 2 HANDER.
The inevitable result being: Bows suck.
Fix them.
DH weapons differ from other weapons, as we can always equip a quiver. Other classes can’t use a OH when using a 2H weapon. Therefore we don’t need 2H weapons with clearly higher damage or stats like other classes do.
At the cost of much lower damage/hit and therefore usually a more difficult hatred management.
Many useless legendary powers is also true for crossbows and 1H-crossbows. I would like to see some more useful variants, too, that’s for sure. But I can’t follow your argumentation here … 
Just put 100CHD as an additional primary stat on all 2H weapons…
I get your point, but on the obverse side of the coin DHs get a mere two daggers (KP, LGF) from the Hope of Cain and 100% of them have been useful for season start for a number of seasons. Not quite at a necromancer 2H level but not terrible options.
The original manticore could drop with 2 sockets: 1 guaranteed + 1 from random roll. Maybe the bows that don’t have a legendary affix could have that instead.
I think a flat damage Increase is the best and simplest solution
The problem with dual socket is Ramaldinis Gift.
It would be better to just put an extra Primary Stat of CHD (dual socket gonna end up with emerald anyway), so you can still roll off the socket, and add with the gift.