Steel Path [Harrow]:

This build is made for Steel Path missions. I equip all the shield buffing mods on my sentinel companion to maximize shield gating and quick shield recharge which multiply with Arcane Aegis. Whenever [Harrow]'s shields deplete from taking too much damage I cast Radial Blind to [Recover] (which provides 35 seconds of recovery time). This ability is also excellent when combined with Condemn for crowd control. Ability 3 keeps [Harrow] and the whole squad supplied with an endless energy pool.

To handle acolytes, simply cast ability 4 right next to them and absorb their damage while doing heavy melee attacks. I use a heavy attack build on [Pennant] for that or [Glaive Prime] with a good secondary weapon. If they aren't dead before the invulnerability ends, then cast Radial Blind (which does work on acolytes) and finish them off.

Mostly I recommend you spam his abilities and have a blast doing so.

There are a number of mod swaps you can do here for the greater or less potent mods depending on your mod collection and your interest in adding forma to [Harrow]. This same build can be used on regular missions but I actually prefer swapping out Condem for [Hildryn]'s Pillage and using [Harrow]'s ability 2 (Penance) for squad and defense point healing.