Your using 4 connections on 20 semi dedicated proxies, they are getting banned, thats why the speed drops. Try 1 connection, 2 is the max, but I would go with 1. Let it ride and you can scrape all 200K keywords in 1 run probably, but I would set retry to maybe 5 just in case.
Alternatively you could break it down into small chunks and use public proxies. The custom harvester can auto retest proxies on the fly, the automator won't do it on the fly. I mean it can be automated, but its best done after a scrape and before another, not in the middle of one. Try turning up the proxy retries on the custom harvester.
How do you define speed? Spending hours/days trying to tweak public or private proxies to give you 5K urls a second, so you can finish your scraping in 10 mins, or just set it to 1 connection and let it go and in a matter of hours or a day you will be done, with no hassle? I define faster as the later, as its less hassle and less overall time input into it.
