If its only one, let him charge and throw/lift him and shot him with shotgun If its more, snipe as much as you can, and when there is some of them charging, lift all except one and focus him while falling back to avoid getting meleed (they do one hell of a melee damage)
As with any enemy, using techs and biotics can really help out (don't just shoot, use those techs/biotics!). As explained before, using throw/lift/singularity can keep them immobile while you hit them. Using a 'poisoning' ammo bullet (radiation, etc... (look at the description of the bullet upgrade, and it will say something along the lines of preventing regeneration)) will take away their 'regen after death' ability. Shredder bullets do a decent amount of damage to them. Overheating their shields and guns will help, but may cause them to charge, which is a danger along.