Going back to my notes...No. They're not good. I just thought they were good 'cause I saw a list with a butt-ton of them. But in reality, what drove the list was triple Dragons. Derp. It doesn't matter what your Battleline is if you're running three Dragons with Empowered Emerald Lifeswarm.
No. Drakespawn Knights are fairly bad. The only thing they have going for them is their 3+ Save, but lots of Heavy Cav. would have that.
My bad.
If you found the right bits, why not? Those Sea Dragon Cloaks are dope.
I've seen somebody try and claim that the (optional) Hand Crossbows, count as Repeater Crossbows. But I absolutely see why some people wouldn't accept that, especially given how effective Darkshards can be.