The Focusrite FAST EQ gives you characteristics instead of frequency bands in the FAST view so you can make certain aspects of any instrument pop-out without worrying about knowing the entire frequency spectrum and what each characteristic is per instrument.
This plugin is designed to visually show you the effect your compression settings are having on your audio signal. FAST view gives you the most important basic controls, and detailed view gives you traditional compression parameters like attack, release, knee, ratio and threshold.
This plugin is designed to help you balance instruments that are competing for space in a mix. A typical usage is the famous kick/bass sidechain technique where you ‘duck’ the bass slightly whenever the kick drum hits. You can accomplish that with any compressor that supports sidechaining, the Focusrite FAST Reveal plugin makes it a whole lot easier.
Should you buy these? I would buy the Reveal plugin and *maybe* the EQ plugin. The benefit is as advertised, they are super FAST to work with, but once you gain experience, make your own presets and more, you can get the same results with any plugin.
The Reveal plugin is the best in my opinion as it makes your traditional sidechain process for ducking instruments that are completing much, much quicker.