Don't assume it's a player's fault...
I know that it's frustrating when we have performance issues. It's been especially rocky since we moved to 1.10.x packs because the amazing tools that help servers with performance were not in a finished state in 1.10.x. The tools are getting a lot better now but there are still mod bugs and server bugs that are causing troubles.
I would guess that if you are experiencing big lag when a player logs on, it's a 90% chance that, on investigation, we will find that it's related to a bug. That means it's not the fault of the player. There's that 10% chance that people do stupid things such as have auto mob killing without figuring out a way to keep items from collecting on the ground. But, it's much more likely that there's a bug.
So, report in #help on slack when you think a specific base is causing troubles, or a specific person, but don't accuse the person. Keep your comments helpful. It's easy to end up with a negative culture in our chat and teamspeak. Let's all remind each other to not get personal.