Been solo mining for a few hours now
...
...
I figured it out.
I think even with correct algo, with solo mining you see no stale rate until a block is found,
and perhaps network connection is all the time equivalent to 90% stales and there is only
very small chance to get the block. No way to know it.
So, pool are a necessary middleman.
Of course, if you can find valid block every 10 minutes...