I would love to see some decent justification for why the Taurin are in the Horde when they seem to have more of an Alliance attitude. Speaking as someone who much prefers playing Horde.
Probably because the Alliance wouldn't take them.
Same with the Blood Elves, really.
The Tauren are with The Horde because Thrall helped them relocate to Mulgore, where they're now based. It helps that Cairne Bloodhoof was Thrall's best friend and closest ally. The Blood Elves joined The Horde with The Forsaken's help because they felt betrayed by The Alliance.
I'm sure that the Tauren could have joined The Alliance if they really wanted to as they're quite close to the Night Elves and their beliefs and culture aren't incompatible with The Alliance.
EDIT: Also, I swear that having the players take down Hellscream was only because Blizzard failed to realize that the fans HATED him. I honestly think that Blizzard wanted us to like him and accept him as Warchief, especially with them going out of their way to have him do things that are closer to what Thrall would have done, despite being completely out of character for him.
Not to mention that it was absurd to hand that unstable asshole The Horde in the first place. If Thrall was being as smart as he normally would have been, he would have handed the title of Warchief over to Cairne as he was The Horde's second in command, Thrall's best friend and greatly respected among the Orcs. There are only two explanations of Hellscream being named Warchief: 1, Blizzard honestly expected fans to like Hellscream as Warchief or 2, Blizzard colossally fucked up writing that idea.