You're right that there's something wrong and it appears to be related to block propagation speed from the pool which would lead to more orphans and possibly lost blocks entirely.
I've been monitoring block change speed at pools here:
http://poolbench.antminer.link/
and there are some occasional glitches that are unique to slush. Every so often he'll get a block like Block 388165 and the pool will issue an update but no other pools will see the block for a long time afterwards meaning it hasn't propagated across the bitcoin p2p network. My pool was the first one to see his block and propagate a block change but it was 17 seconds later.
Found by slush
I've been monitoring block change speed at pools here:
http://poolbench.antminer.link/
and there are some occasional glitches that are unique to slush. Every so often he'll get a block like Block 388165 and the pool will issue an update but no other pools will see the block for a long time afterwards meaning it hasn't propagated across the bitcoin p2p network. My pool was the first one to see his block and propagate a block change but it was 17 seconds later.
Found by slush
Code:
1. us-east.stratum.bitcoin.cz:3333 2015-12-13 05:29:36.698000
2. solo.ckpool.org:3333 2015-12-13 05:29:53.658000
2. solo.ckpool.org:3333 2015-12-13 05:29:53.658000
i took a good look at that site and ill tell ya what stands out to me.. I don't see all slush stratums on there. Would that site show private stratums that slush has or do btc pools have to install an api for that site to poll the data?.. reason i ask is a few months ago i got an email from slush stating that i was one of his top miners. Which at the time i was at slush back in late 2014 early 2015 i was at 80 th/s. In that email he gave me a private stratum port to mine to. I threw my s4's to it as they were easiest to swap to it. And i swapped a few s3's. What im wondering if this new private stratum is to blame here. I dont want to give out the address but i wonder how many got that email and just how much of slush hash is on these new private stratums.. What he told me was that it was for ddos protection. Also i know he is using This relay network. not sure if its reliable or if its also part of the issue? http://bitcoinrelaynetwork.org/ http://bitcoinrelaynetwork.org/stats.html
The relaynetwork seems to be working perfectly well for the rest of us (and is a real boon to mining pools). Regardless of how many and where his stratum servers are, the issue lies in getting the block out to the network which is far more important than getting a stratum update out to his miners, or the block gets lost. I thought it might be isolated to a particular location but looking at more of those blocks I see it can happen sourced from any of his stratum server nodes. In the last 2 blocks checked on poolbench, one of them still took 8 seconds to get propagated. If you look at other pools, it's usually in the order of hundreds of milliseconds by comparison.
the fucked up thing is neither are finding blocks(the solo miner or slush) lol i look thru last several hundred blocks i see no solo miner. 
.. if it comes back around then great but i will keep my eye on this and be the first to say i was wrong about this pool..