It's known that Eranikus and his brother Itharius were entrusted by Ysera to deal with the corruption of the troll god Hakkar the Soulflayer and prevent him from escaping the Sunken Temple created when Ysera smashed the Atali and their temple below the waters in the Swamp of Sorrows. What is at present unknown is the connections between various vile forces: is Hakkar an old god, an agent of one, or otherwise related to them? How does he relate to the Nightmare? Somehow, while Eranikus managed to destroy the god's physical form, he was corrupted and his dreaming shade imprisoned within the temple, to be later found by adventurers and destroyed, freeing his chained essence. (To step out of lore mode for a moment, the fact that the quest line just stops dead in Winterspring is annoying to me personally.) Later, a vision of Malfurion Stormrage himself reveals that Eranikus' corruption is tied to that of the Nightmare, which means... what? How does this relate to Hakkar? We can speculate, of course (given recent events in lore - I am now linking to two spoiler heavy reviews of the new book Stormrage so if you click these links it's your own fault, I warned you) but in the end we keep getting hints that lead to figures that then hint at deeper evils offstage.
Whatever the Green Dragonflight is facing in the Dream, it's powerful, malevolent and can warp even the strongest members of Ysera's brood (the aforementioned Dragons of Nightmare and even Eranikus himself): it's understandable that with an enemy like that or old gods trapping members of the flight in Ahn'Qiraj, the greens didn't pay too much attention to the events of the First and Second Wars. What interests me (and what I've never really seen answered anywhere) is this: do orcs and draenei in Azeroth go to the Emerald Dream when they dream? Are they somehow 'outside' the green dragon's jurisdiction or in coming to Azeroth have they made themselves part of the spiritual blueprint of Azeroth even though they were never intended to be a part of it? Certainly the green dragons haven't expressed an opinion on this.
We know that Ysera was restored to her full power following the destruction of the Demon Soul in the great battle with Deathwing outside Grim Batol, when she finally listened to the entreaties of Korialstrasz, the consort of her sister Alexstrasza. (Just as is the case with Malygos, it's unclear if they actually are siblings or just call themselves that.) It's also the case that there was little to no reaction during the Legion's invasion of Mount Hyjal during the Third War, even though the druids themselves responded and Malfurion chose to yet again blow up something hugely magical to stop them.
In the aftermath of the world tree's destruction Ysera refused to bless the replacement planned by Frandal Staghelm, perhaps due to his disrespect during the War of the Shifting Sands, a general desire to avoid giving the night elves another giant magical thing to blow up, or even possibly related to the ultimate fate of Vordrassil in Northrend (since Ysera and her brood were aware of events there due to their role protecting the Great Tree to the Emerald Dream in Crystalsong Forest).
At present, while Ysera appears to sleep in the Emerald Dragonshrine in Northrend, but her flight is far from resting. Between battling the corruption of the Nightmare, being kidnapped and tortured by the Scourge, dealing with Blue Dragonflight forces that recently laid siege to Wyrmrest Temple or guarding various sites of importance to the Dream (such as the aforementioned Great Trees) they're a remarkably active bunch of sleepers.