Torrential needs to have an end game to talk with a pony? 

I kid. Truthfully, he is there for a few reasons, but the main one is because despite everything that has happened, Torrential still views Applejack as a farmer and thus feels a need to look out for her well being (After all, Applejack is an awesome farmer and that is something worth risking her swinging a warhammer into his head to touch base with). Besides, he has been traveling in her realm these last few months; least he can do is drop in and politely say 'Hi'.