I have seen some posts on Reddit about the difficulty of Hell's Precipice as a Prophecies-only account, where only henchmen are available. Some users there help new and returning players who are unable to complete Prophecies. While henchmen bars were revamped in 2009 (and I think the Prophecies ones are especially viable), Hell's still poses a wall to some players in NM without skills and heroes from other campaigns, PvE-only skills, or consumables.
I have decided to see for myself what HM with henchmen would be like, not only for Hell's Precipice, but for Ice Caves of Sorrow, Iron Mines of Moladune, Thunderhead Keep, Ring of Fire, and Abaddon's Mouth. The first four were fairly simple. I took an IMS for the bonus of Thunderhead (Illusion of Haste), and the other bonus objectives were just detours with no added difficulty (the few Mursaat in Ice Caves where henchmen are not infused were not that hard). The end of Abaddon's was annoying with those incoming Mursaat, but fair when played slowly. Hell's was another story.
Sparks of the Titans were really challenging. I was able to handle two of them and a Titan or two, but the one or two groups where three of them are present had me retry the mission numerous times. The one time I was able to make it to the three rifts is when I completed the mission, so at least retrying took little time.
I switched between Domination and Illusion for the previous missions. For Hell's I found that melee Titans were hard to handle without Ineptitude, so I opted for that with some targeted interrupts for Sparks. Dunham has Power Block; I had to track that shadowy animation and focus on the rogue Sparks (I also tried to Arcane Mimicry his PB the one time I played with Energy Surge, but I found that less ideal). There is no way to spread henchmen without letting them take damage and do it on their own, which also meant that deaths were common. DP is easy to negate though as XP is absurd versus level 30 foes in HM. Many bosses make it easy to rely on the henchmen's Resurrection Signets too. Lina and Mhenlo had Restore Life for when I had to retreat and res a couple of times. I had the Sparks target me first (with the hope that Lina would cast Protective Spirit and the excellent Aura of Faith), and only then let my party engage them. I found that allowing the Sparks to remain elevated and just outside of compass range would mean that they would only cast on the frontline that come within their range. Devona's knockdowns were also exceptional.
For the bonus, it was easy to save the Seer with Ineptitude and to pull the three Lords one at a time.
It took me close to an hour and I think it would take less than 40 minutes with some practice. Panic may work well when rounding up enemies, but at some point I thought Ineptitude too good to try anything else. I elected not to use a defensive set for added difficulty, just my classy Ghostly Staff (well, I AM a Mesmer). As for my bar, Ineptitude is the only Prophecies skill, and the other seven are Core.
I had a lot of fun and would recommend this self-imposed ruleset for something different.