Suppression is a GREAT ability that I can see being almost necessary in elite campaigns, but I think that it should be tweaked from how it currently works. For those who don't know, Suppression causes an enemy to be mesmerized, which is like being stunned except any damage done instantly breaks the effect. The purpose is that you can fight less enemies at one time and increase your chances of survival.
In Star Legends Suppression is the only mesmerize ability. It lasts for 6 seconds and has a 15 second cooldown. That means that it would take THREE engineers on rotation to maintain a suppression hold. In every game I have ever played that includes mesmerize effects the mesmerize effect lasts FAR longer than the cooldown of the ability. What is the reason for this not being the case in Star Legends? Absolutely nothing is gained by chain mezzing as you can't kill the thing and it can't kill you.
Here is my suggestion: Increase the duration AND the cooldown significantly. Perhaps make the duration 30 seconds and make the cooldown 25 seconds. Now you have the ability to take things slowly but safely. In the current campaigns this probably wouldn't be used much as a full group can just storm in diablo style and wreck things, but in elite campaigns proper suppression use would become key. With the long duration, a well coordinated team could survive. With the long cooldown, the ability could not be abused to rush bosses, poor placement when casting the ability would be disastrous, and it couldn't be used to save a group who pulled adds. In addition, if someone breaks the mez at the wrong time they are screwed because the cooldown is so long.
If this is deemed too powerful, make suppression cause a LOT of aggro. Now there is an additional punishment for screwing up... break mez and your healer is in for it.