Rushing (in HC) isn't sooo bad since the only tough place to complete is CS in Hell. It's tough in NM, too, at high p settings (no I'm not joking! - at the very least it's slow). I always bring a barb for BO so one less mule in NM/Hell, basically
I'd estimate something like 3 hours to get everyone there very very safely, then ~5-10 mins/game to collect individual forges (more time as well for crafting in-game). You won't need to mule every game since you won't get worthy runes very game.
So maybe 4 hours in HC. Honestly probably pretty comparable to LK, if I had to guess. Ko, Lum, Fal are the most relevant runes... are there some I'm forgetting from NM/Hell
(edit: forgot about NM forge collecting but that is obviously much safer on /p1 so should be a bit faster)
edit2: BTW I've done this about a dozen times in 1.07. You need to abuse quest glitches/shortcuts in Act 2 (mule on staff in NM and Hell, only one char needs to talk to Tyrael), Act 3 (skip to Meph, only one char needs to be present for kill (does it even have to? I forget)