The writing is just awful. If everyone acted in character:
-Sylvanas wouldn't have started a war immediately, she would have tried to manipulate the Alliance if she truly wanted to cause problems. She's not above torturing a zombie into killing his family in their sleep but she never thought to try similarly dastardly and manipulative things before going right for war?
-Anduin would have approached Talanji and Zul while they were captive just like he did Saurfang, he probably would have even offered to help Talanji with her issues and dissuade her from asking the Horde for help - not lock them away and risk drawing the ire of the "most fearsome fleet on the seas" the Zandalari had
-I don't think ANY of the Horde leaders would have agreed to jump immediately into war. Garrosh pounced on Theramore, Sylvanas pounced on Teldrassil. Not a SINGLE Horde leader stopped to say "hey wait a minute, the alliance and horde are the closest to peace they've ever been, are you fucking serious right now?"
It's just getting sillier and sillier as the patches roll by.