As for why I asked about it here rather than email the pool owner directly, I thought an answer to my question would be of interest to others. I know many feel the same way I do about the totally dysfunctional vardiff strategy usually implemented on Cryptonote pools and it is only by complaining about it loudly and often that anything will ever get done - after all, there was a reason you implemented fixed diff, no?
You are right. Default vardiff config does not work properly. But it is possible to optimize it. I am currently trying to optimize irdpool.eu.
Could you point your miner to irdpool.eu and tell me what do you think of my configuration?
Thanks!