Found a quite easy path to get up to the Lightning Forge on Isle of Thunder.
In this first picture you can see the rock I used to run up. It's actually quite easy and surprised me it was right there. It's much easier to jump on the rock with Path of Frost but is possible to get up without it:
https://i.imgur.com/Mw53ZwNh.jpg
Here's where it is on the map:
https://i.imgur.com/CsQY82Nh.jpg
Here's a picture of me in the forge, I was even able to kill Itoka and get the recipe to make Lightning Steel. Not sure what his respawn timer is or if he will respawn before the island is opened, he hasn't in about an hour. It's possible he won't respawn until stage 3 is completed.
https://i.imgur.com/IpMNgXgh.jpg
Upon completing the quest on a book sitting on the forge you get pages that teach you how to make the 6 reforged weapons from BC. I can make them all right now and lightning steel.