Those pesky orcs

So I've been playing the Blade of Galadriel DLC for Shadow of War recently, and I re-discovered one of those really annoying things that can pop up in these games from time to time: an orc who's immune to just about every kind of attack available to you. One of the gear missions in Seregost requires you (Eltariel) to track down and kill an orc who has a bow or cloak (I forget now), and he's (naturally) immune to her elven Light abilities. He's also a Defender, which means he's also immune to front-facing melee attacks. He's also immune to frost, beasts, poison, and arrows. He's also a vault-breaker and too wily to leave his back exposed. That just leaves executions and fire. Now as Eltariel, I don't have any fire-based attacks (at least not yet--I suspect there's a gear set I haven't collected yet that may grant one), so I'm left with the goofy option of detonating campfires or shooting barrels of grog, sneaking in a quick stab and then retreating until I can find the next thing I can immolate--all while ensuring that I don't get TOO far from my target captain, lest I fail the mission. It took me roughly 45 minutes of running around and engaging in these shenanigans before I finally succeeded in killing him. Talk about trial by ordeal!