I have cleared every mission and bonus in every campaign using parties of just henchmen and/or Heroes. In Factions, missions that required two separate parties obviously created problems, but I still stuck to HnH as much as possible.
In an effort to illuminate others' understanding of the usefulness of henchmen as compared to (most) PUGs, I present the following list of "hall of fame moments". Note that when I say "all-hench" or "Hench party", it means exactly that - only henchmen. Not Heroes. If I say "all AI" or don't specify then it means Hench and Heroes together.
- Completed Gain Olias with six characters using an all-hench party. Henchmen are Level 10 at Lion's Arch. Margonites are Level 24. Pwn't. (Hard for a Monk though)
- Completed Sunspears in Kryta with three characters, using all-hench party.
- Did The Last Day Dawns with a four-man party; Heroes only (since hench are level 3).
- Got Zenmai on six characters using Hench parties.
- Completed Sunspears in Cantha with two characters, using all-hench party.
- Did The Captured Son with an all-hench party.
- Did Quimang's Last Stand and related quests with an all-hench party.
- Got Masters in Zen Daijun on the first try with my Ritualist, all-hench party.
- Did An Unwelcome Guest with an all-hench party.
- Completed all missions, on both Alliance sides, at the Masters level.
- Took out an Evil Mime at level 8!
- Cleared all the "Difficulty: Master" quests on Istan as soon as they were available.
- Killed all the Corsairs in "What do you do With a Drunken Shauben?"
- Took on the Warrior and the Ritualist bosses in Barbarous Shore, along with all Corsair groups in the area, at the same time...and lived to tell the tale with 60% DP!
- Cleared out the entire Fortress of Jahai with 60% DP.
- Took on an Immolated Djinn, Acolyte of Dwayna, and many Kournan troops, all at the same time...and survived with less than 60% DP.
- Completed all missions at the Master level.
- Did Battle of Turai's Procession with myself and just two Heroes.
- Capped Searing Flames with no deaths from Korr, Living Flame.
- Capped Vow of Silence without using Junundu.
- Capped all the Dervish Avatar skills.
1st time Prophecies - Prior to Ascension
- Cleared Nolani Academy by opening the front gates; all-hench party. (fun)
- Saved Benji Malaka in D'Alessio Seaboard with an all-hench party. (frustrating)
- Rescued all the Chosen in Divinity Coast with an all-hench party.
- Completed all Crystal Desert missions and bonuses with an all-hench party. (easy...mostly)
1st time Prophecies - After Ascension
- !Killed Glint with an all-hench party, on the very first try too! Thank you, Wild Blow...Ele changed to Mesmer secondary and beat it on second try; Ranger finished without any special build. Monk used all Ranger skills, Assassin used a standard build with Wild Blow.
- Slew the Mursaat in Ice Caves of Sorrow without being Infused, in an all-hench party.
- Fought my way to the Seer in Iron Mines of Moladune to get Infused, using all henchmen.
- !!Finished Thunderhead Keep Mission and Bonus using only Henchmen, Four Times!! (proud of myself) I've subsequently done it several more times, "just for fun". My excuse is it's a good place to level up pets. ;)
- Cleared Ring of Fire, Abaddon's Mouth, and Hell's Precipice (mission+bonus foreach) using only henchmen. Lich Lord was rather easy.
- Finished Defend Droknar's Forge with only henchmen. So much easier as a Fire Elementalist...
- Capped all Prophecies and Core elites using a hench party.
- Finished all parts of To Sorrow's Furnace quest with an all hench party: Summit Slaves, Kilroy Stonekin, Unspeakable, Unknowable, Noble Intentions, and Noble Intentions Plan B. Really long, really hard, but definitely worth it.
- Finished The Final Assault and The Forge Heart with Heroes and Henchmen. Easy.
- Cleared every Zaishen Challenge with the Zaishen henchmen.
- Cleared up to about ten rounds of Zaishen Elite with the Zaishen henchmen. Finally died on an ~8 Trapper team.
- Cleared the first floor of Tomb of the Primeval Kings with the Zaishen henchmen.
- Explored over 90% of Tyria with just henchmen - including high-end areas like Mineral Springs and Snake Dance.