Is Dash so good that it can surpass BTC ?
Yes, it is.
So what happened with all the accusations of the premining stuff, and also all the potentially exploitable weaknesses given the masternode model, which would be easy for authorities to neutralize?
How does this scale compared to bitcoin?
The instamine (not premine) is a non-issue, obviously, the creator should enjoy the fruits of his own creation. The masternode weaknesses that were described do not exist.
Dash has an elegant solution to scaling which involves the masternode network. A DAPI (decentralized API) will be created that links to the masternodes, who host full copies of the blockchain. The blockchain can scale indefinitely because owners are incentivized to keep up with the growth. And the end user will have full access to the blockchain instantly from any Evolution device (which is any device). Always going to be lots of room, enabling fast and inexpensive transactions. Hope that helps you!