It was in no shape to fight back, and yet the alliance decided to not enact on this golden opportunity to end it there. The horde should have been dismantled and carved up for the winners, for the spoils of the war go to the winners. An occupation council should have been instated, and a deindustrialization process to prevent the horde if ever reunited to ever wage war again.
Of course occupational duties take a heavy toll so occupation duties will have to be upheld by troops native to the land until the dehordification process is complete.
The fleet of the horde, whatever is left of it, will be divided up to the winners. So will the rest of the stockpiled supplies and vehicles. Any blueprints will be sold off.
Orgrimmar will be turned into a free neutral city, ripe for trading with road connections to Azshara and Durotar, plus the harbour next to it. So will the island in the middle of Azshara. Silvermoon city will be repaired and grant a concession port to the alliance. The tauren had it hard enough so they'll be left alone and get help with their quilboar problem.
The horde constituents will also have to pay a sum of money and resources for many years forwards to repay the damages they caused the alliance.