As far as I've found there are only two ways to get to the forge area, the jump near the Thrinn area, and jumping down from the metal walkway. I'm not a great platformer to be sure, but one way guarantee's someone is left behind to work the moving platform controls and the other has an athletics barrier that also means not everyone could make it, so the only sure way to bring the whole party into the forge area Edit: (At one time) is through the pseudo-canon portal. And I maybe the only way to return to the first area is through the jump.
This particular fast-travel 'cheat' also bothered me so I spent some time trying to figure out the "right" way to get there without success.
I was doing this as a low str halfling so my take might not be the best.
If it weren't for the fight that the metal walkway leads to I guess both methods make for a viable way to get everyone into the forge area.
As a mostly unrelated issue, I'm kind of upset that mage hand can't operate the platform controls. That's exactly the sort of thing mage hand should be used for.
