We can see here in bitcointalk which are the most trusted casinos,they are also usually in their signatures. We can be sure of the casinos when we already play,we can see if its the rolls were only benefits the casino or not. But in the end,without proper control of playing the casino will always win.
As when they proccess your withdrawal faster than any other casino it is mean they have good intention.
And a good security system there to allow your money to get released asap.
Even if a casino has instant withdrawals they don't have much in their hot wallet and hence you have to trust the owner when you win big and 90% of scams happen when user won something big.
For example when you wait for 24 hours but not yet get your withdrawal , then keep waiting again for another 24 hours until there is no end to wait.
Then they are confirmed as scam , that moment what i think about the faster withdrawal the lesser possibility a casino to get out as scam.
You're absolutely right, delayed payments without any notifications or reasons automatically suggest they might be a scam and not a trustworthy casino but must you go through such a hell of a time to determine their legitimacy? I think it's better to read around a little before committing your money to a casino. User reviews are a good starting point. That should help you make an informed decision before anything else.