Try disabling "Live Traffic"
Also: Go to Wordfence options. Scroll to the bottom of the page and find:
Update interval in seconds (2 is default)
Set this update interval to something like 30 seconds (just enter the number 30) which will cause a hit every 30 seconds when you're watching live traffic. That should keep your web host happy.
http://wordpress.org/support/topic/increased-load-on-the-server?replies=4