Hmm...well, here's how I see things.
I'll give your inclusion of Pariahs a thumbs-up, because I've always liked the concept, and because the scenario you describe actually sounds like it might accentuate their strongpoints. Conversely, I think that one of their primary functions against a Marine army would be as counter-charge units, given that they are still very resilient to standard attacks, and because on the charge they can kill entire squads before any powerfists are brought to bear(assuming that the squad isn't a full one and has been whittled down some. Don't get me wrong, I'd still advise caution, but when the Marines come to lock horns, it would be foolish to waste their primary weapons' main strength by ignoring the enemy's power armor. Understand, I only suggest charging units of seven Marines or fewer, and that's with a full squad. There's another thing right there: I'd include a full squad of Pariahs; I'd fully commit, given how many Warriors you've chosen to take, giving you a substantial fadeout advantage.
It is a strange scenario, it's odd seeing how radically conditions can change with a mere twist of objective. Typically, I'd say that you seriously lack firepower, and would want to soften up the Marines before they reach you in head to head. However, in this case it would seem that any ranged firepower is only likely to make use of its range for a turn or so before the Marines are already within range.
Nevertheless, there is still one additional change that I think you should make. Your Lord is outfitted strangely, and given that you may end up defending a wide expanse(I don't know how the bunkers are set up), it would benefit you to come with two Lords to the table. I would outfit one for a combat role, as well as to provide an additional Resurrection Orb. Whichever Lord you decide to give the NightMare Shroud should not be intended for close combat, since it can't be used in melee. To use them in tandem, it would make sense to give the one Lord a Phase Shifter, Res Orb, Warscythe, Gaze of Flame and Phylactery; while giving the other Res Orb, Nightmare Shroud, and a Destroyer Body so that he could provide NightMare Shroud wherever it was needed, especially if you wish to use it in conjuction with the other Lord's Gaze of Flame. These are simple tricks though, the primary purpose is to be certain that you always have a Resurrection Orb nearby.