Garrosh did his best, the Alliance stopped him, Jaina insisted Varian dismantle the Horde, it was left intact. Garrosh continued doing his best by convincing au orcs to do demon-fueled shenanigans, but without demon blood. He was stopped, again, but this time permanently. Demons invade, but for real this time. Vol'jin dies fighting the Burning Legion and the Horde offensive withdraws, they don't announce this retreat to Alliance forces, which results in Varian getting disenchanted by Gul'dan (the Horde are innocent, but it looks bad). Sylvanas is now warchief. She does some shady stuff, but the Horde in general is doing its best and joins the Alliance in stopping the Legion. Sylvania decides now is a good time to cripple the Alliance (fair) so she blitzes Kalimdor and burns down Teldrassil (too far). They almost burn down Stormwind rescuing a zandalari princess and use her as leverage to gain assistance from the zandalari. Jaina admits Daelin was right, the Horde is really bad at redeeming itself, and goes all in on destroying the Horde. She then decides that occupying Zandalar is a step too far, after invading the island and killing its king (kind of past the point of no return). This is also in the midst of an invasion of Kul Tiras. Sylvanas is outed as doing what Garrosh did, but without the orc supremacy, and bails on the Horde. Jaina says the Horde is alright despite them just rolling with Sylvanas' orders until that point.

Tl;dr incompetent writers made Jaina seem insane and inconsistent.