Pages load slow (15-20sec) on Multisite WP

We are running around 35 sites in our multisite WP, using IIS on Win2008R2 Server.

Site load times is varying, sometimes loading in 5 – 7 seconds, other times 15+.

We expect our sites to load in 1-2 seconds max.

Server resources are no where near max capacity, nor is the pipe to the internet. We use dedicated fiber connection.

Example of slow load times http://outlawmusic.ca/

We are in the process of testing one of our sites in a single WP environment.

Looking for any suggestions or help regarding multisite WP.

Here is a list of plugins we have installed:
Breezing Forms
Comment Guestbook
Contact Form 7
Contact Form DB
Custom Facebook Feed
Easy Table
Events +
Google Analytics
Google Maps
Infinite SEO
Insert HTML Snippet
NextGEN Gallery
Revolution Slider
Social Media Tabs
Surveys
Testimonial Basics
Tweet, Like, Google +1 and Share
Viper’s Video Quicktags
Visual Form Builder
WooCommerce
Woocommerce Advanced Bulk Edit
WPBakery Visual Composer
WP-FileManager
Content Dock
Custom 404
Disqus Comments
Email Forms (MailChimp)
Facebook Comments
Google Analytics
Olark Integration
Slider Revolution
Smooth Scroll
Soliloquy
Terms of Use
Under Construction
Video Lock
X – Shortcodes

Themes Installed:
Duotive 5ive
Helix
Metro 3.0
theme52834 (Tobacco)
Twenty Eleven
X
Default WP 2011,12,13,14,15