The most of staking rewards go to top addresses (especially #1 and #3), even 4-5 times in one hour. I haven't got any rewards for 9 hours though I have a few thousand of DMD, about 10 ready to staking piles and status "staking is active".
let me disagree with this.
I even spread a screen of my wallet.

You see, this morning I found a block, as was the case yesterday.
I found (2) blocks yesterday and I only have (4) piles of 200 dmd each. So staking is working as it should. I believe you just have to leave your wallet open to compete. If you close your wallet at all I believe it removes your chances of stakes. Also, if you freshly opened your wallet it will take some time to compete with all of the wallets that have been open.