I know what a lot of people are probably thinking already - this is abusable. 8 accounts and you've got free crafting costs. I know this, and it's one of the reasons i've been bouncing this idea off a few of my friends already. I've thought of ways around this.

Simple solution - no matter how many players are in the "pool" of mist, there is always a cap of 100. This means that if me and a friend go down 5 levels (assuming we don't die), we each use 50 mist, and each have 50 left over. With this, we could pool those 50s together and allow one of us to craft something. This is no different than him tabbing me beforehand and me having the 100 anyway (or vice versa), and it'd help the issue of wanting to trade mist to your friends without crashing the energy market.

Secondly, this mist pool of sorts could also be used for other functions - couple of levels before the core, but we're not doing so good. He's got 6 energy left and i've got 7 - currently, we both go back up to Haven despite having more than 10 total. With this, I could tab him then go up to Haven, but still pay the remainder of his fee (or him to me) leaving me with 3 energy left over (since he's going down, he'd pay his full mist before mine is added to his fee).

And thirdly, although this is only half-related, why can't we tab people before they join a party? Say I got a friend who's got less than 10 energy left, and he wants to join me, and I want him to join as well. But he can't, because he doesn't have the 10 energy to pay the fee. This even applies in levels with no fee (terminal, emberlight, moorcroft, tier 1 party lobby and mission lobbies). Even if I have 100 mist, and am willing to pay for him, I can't, despite the game offering "a way to pay for friends" of sorts, you can only pay once they've already joined. Maybe some sort of energy sign next to invite if they have less than 10 energy, bringing up a "this will cost you 10 energy" prompt which, like others, can be dismissed for ease of use to anyone who is used to it if they prefer. Energy would only be taken from the inviter if the invited person agrees to join. "No thanks" won't charge mist, and hiding won't charge mist until (if) they decide to click join later. Obviously, this wouldn't apply to joining people, only inviting them. We don't want unwanted energy drains, naturally.
Also the ability to re-invite someone if the invite failed earlier (not logged on, not enough energy) would be appreciated. Clicking "no thanks" would prevent re-inviting them, as would if the invite prompt was still open (or hidden)