The World Tree once provided the Night Elves with the energy to fight and defend their lands to the best of their ability. While not a step back, this supplement, an energy vitamin or something similar could prove to be a great way to get the Night Elves out of what appears to be World Tree energy withdrawal, in the course of the story since Warcraft III.
The primary counterpoint I can think of is that this may not be safe at first, or at all. Druids trained as herbalists might be key to seeing if this is a viable, workable solution.
Any thoughts would be welcome; I realize this may break the flow of the story and be outright dismissed as not like the Night Elves. To make a case for this idea in general, the Druids of the race can help trees heal and wildlife recover, when they wish to do so. I do not see the NE's saying they should be killed off to better the world. Rather, I would expect them to try to "fix" their race; this may mean growing a medicinal herb, that functions similar enough to the World Tree at full strength long enough for said tree to recover and help the race it empowered for so long.
This solution may lead to dependency, however, since said dependency on the World Tree appears to be greatly hampering the race now, any alternative at least in theory may be better than not having what they are used to. Of course, this may also work against the Night Elves and lead to other issues.
Edit: I'll add what I seem to have forgotten: Wisps gather wood and seem to convert the tree's effort to grow into lumber for the Night Elves. While there are not many Wisps around now, there may be ways to fix that. If there are more Wisps, there's more energy in the NEs' supplies; perhaps some can be directed into a reverse process of getting it, creating a fruit, berry, or something useful that can safely be ingested to supplement the energy NE's are as individuals used to having day to day, before the World Tree was injured?