What can't you H/H?

Yeah pretty much possible to H/H everything where they're allowed to enter, including SF and Dungeons HM. Hell according to the wiki, even slaver's is H/H'able in HM even though I have no idea how, NM in there is already nightmarish in there.

edit: I'll make an exception, I have my doubts that The Eternal Grove is doable in HM with the masters reward due to the shear dificulty of that mission. did it on HM yesterday, piece of cake. Flagging the 2 monk henchman and the domination and cynn on the south. Placing you and youre hero north. The hench will take care of their part, only thing you should watch is getting rid of the turtles in the time that there are no enemies at your side. Did it without any comsumbles or whatever.

Well maybe areas in the vortex may be proven a challenge on HM. There is a quest there that i think is impossible to H/H (some master quest).

I personally would hate to do Troubled Keeper quest in HM with H/H. Never tried, though! Only way I could figure that out was microing a shadow form hero to keep a side occupied... that was before whatever round of nerfs, but it should still be doable.

I think, literally anywhere is possible H/Hing with enough time investment. For example, duncan HM is obviously do-able because of ebon sniper. Sure it might take 10 hours... but that's hardly different than how I did vloxen, which is to say, pulling foes halfway across the map Please H/H Tihark Orchard.

Please H/H Tihark Orchard. LOL someone just did the daily mission!!!

FWIW, I HM masters that on 6 different chars a couple days back, every single time less than 10 minutes total (timed using a cupcake - LOL!). I used to dread that mission because of the mime, but after an hour (and 420 copper coins) I think I got him down pat...

Slavers Exile HM? Not a problem.

Is there even any spot there from where you could pull groups? I've tried that corner spot but it was useless everything is still aggroed eventually. Haven't tried again since. I'm not sure where I pulled to, but when I did it a few days ago with a friend we managed to find a spot that we could pull to without attracting other mobs.

Anyway, I can't think of anything that I haven't been able to H/H at some point or another. Eternal Grove I never want to do again by myself. Vloxen and Rragar's were messy but that's cause I didn't plan too well. Duncan HM actually went more smoothly.

I think, literally anywhere is possible H/Hing with enough time investment. For example, duncan HM is obviously do-able because of ebon sniper. Sure it might take 10 hours... but that's hardly different than how I did vloxen, which is to say, pulling foes halfway across the map I'm inclined to agree that if you can take henchmen somewhere, you can H/H it. The builds required may be quite specific and playing it may be very difficult, but I suspect it's possible.

I'm not sure what magic the ebon sniper is supposed to do for Duncan though. Though I seem to recall having seen screenies of Jeydra having H/Hed Duncan HM.

I'm inclined to agree that if you can take henchmen somewhere, you can H/H it. The builds required may be quite specific and playing it may be very difficult, but I suspect it's possible.

I'm not sure what magic the ebon sniper is supposed to do for Duncan though. Though I seem to recall having seen screenies of Jeydra having H/Hed Duncan HM.

Since I made the first post lots of areas which used to be hard are now simple H/H's, such as Vloxen's, Duncan and Rragar's. I can do almost every area I've tried H/H with a player offensive character now, which probably means so can any other profession. There are two exceptions. Both I can H/H as an Elementalist primary, but not sure about other professions.

Forgewight HM - I had to rely on ER Infusing for this one, not sure if it can be done by other professions (especially one that doesn't have access to Save Yourselves!).
Shards of Orr HM - this one beats my imagination. It can be done with Obsidian tanking / 600 of course, but if there's a reliable way to do this dungeon with more standard builds, I'm not aware of it.

PS: The Ebon Sniper is a rather stupid way of doing things. The basic idea is to have Shadow of Haste + Ebon Sniper + some other kind of defensive skill if you really need it (e.g. Shadow Form). You Shadow of Haste far away, run close, Ebon Sniper, hope you get 900 damage and instakill someone, then cancel Shadow of Haste, disappear to safety and repeat. It's painfully slow, so slow I've never seriously used it, but I guess it works if you have enough patience.