More effective on higher difficulty levels as enemies will gain higher armor values. It's largely unnecessary on Easy/Normal, as enemy armor can be easily shredded with 1-2 Grenadiers or downright ignored.
Combines well with the Grenadier's Holo Targeting and Shredder abilities. The Grenadier can perform squad opening shots to apply these effects for others, while using the rounds to pierce before the armor is stripped.
Sniper Sharpshooters are easily able to destroy mechanical units from long range. They are generally less punishing to equip since snipers do not need protection vests in most cases. Can also feed kill streaks off Kill Zone/Serial abilities.