Upfront sites with wpmudev plugins very slow

This post is not really just about defender, but defender is the plugin that takes up Thebes's most resources.

We have been struggling with client sites that we've used upfront themes and your plugins being very very slow.

Humming bird does ok, but suggests other plugins to help. One suggested plugin says that defenders is a resource hog.

Why is upfront so terribly slow?

How've can we fix? Marketpress USC also unbearably slow as well even on premium Hosting's like Pagely

Please advise