Ranged combat uses a system that takes into account a variety of factors to determine your chance to hit the target. These factors include distance to target, line of sight, and if they are in cover. If an attack lands, damage will be applied after any armor bonuses.
Since enemies will also take advantage of cover, explosive weapons or certain grenadier class powers are very effective for destroying this cover and exposing your enemies.
While explosive weapons tend to have a reduced impact on enemy health, they are great for shredding armor, which is represented by a yellow meter at the end of an enemy’s health bar. Explosives do not use a percentage and always hit, as long as the enemy is within range. Try to place explosives in an area to hit multiple enemies at once.
If you’re taking on a number of armored foes, hitting them with a well-placed grenade before cutting them down with standard weapons is a highly effective strategy.