Suppressing Fire gives your guns more stopping power against weaker enemies while Focus is active. It is a Tier 2 Ranged skill that helps you halt a rush of Swarmers or humans in slow motion.
It is a middling pick. It helps if you use Focus on groups, but Crowd Control usually matters more.
Focused Shot, Crowd Control and Under Pressure.
Use Focus on the leading enemies in a rush. Stopping the front runners slows the ones behind them.