We've (we=some of the Defold core team) spent a good time with a bunch of Cocos2D core devs at GDC. Each tech has strong sides and features in development. Currently Defold is a young free tech mostly used at King. But this improves at a pace of a solid couple of hundreds per day.
This is an ambitious statement =] But yes, the engine at the current state may be decent for certain use cases. We're working to make it better, obviously. Give it a try at a game jam neat you. Or at the upcoming Ludum Dare.
Yes. So King uses the engine internally, right? The tech is driven by the Blossom Blast Saga team and by another 5 internal teams using the engine. In fact, the engine team and the games team reside in a same room, and are isolated to a separate building from the other teams. A close collaboration in a very productive environment. From where I am ;-)
Oh.. so the art/assets pipeline is pretty much dictated by the internal teams. But feel free to use the engine and explain on Defold forums of the good and the bad. We'll be happy to listen.