I've heard a lot of people say that, but I'm still having problems with a single tab locking up the whole browser for 5-40 seconds on FF 53.0a2 Dev Edition with

I've heard a lot of people say that, but I'm still having problems with a single tab locking up the whole browser for 5-40 seconds on FF 53.0a2 Dev Edition with e10 and process count at 999.