https://www.reddit.com/r/EtherMining/comments/6inwni/psa_if_youre_mining_with_dwarfpool_or_f2pool/ Tl;dr: you're mining empty blocks to trick the ETH network into restricting the gas limit and are causing extreme transaction latency. Notice that 15% crash that almost brought ETH back under $300? Yeah, two of those reasons are reportedly pools you might be mining with. Here is a post linked over at /r/ETHTrader with more information: Link Dwarfpool has previously addressed this here, however it seems to have not accounted for current behavior which is claimed to be responsible for extremely long transaction times. The DoS attack which was the reasoning behind the switch was remedied at the protocol level months ago and this behavior is no longer necessary. Possible evidence of F2Pool prioritizing their own transactions through a similar methodology has been uncovered as well. Until these pools stop intentionally sabotaging their own users, do not mine with them For a list of reputable pools, please visit the wiki. I have since removed Dwarfpool as recommended and have never included F2pool.