After aiding in the battle against the new Prime Evil, i'd assume Tyrael would be able to call in a few recruits. And before you pull the 'but only the nephalem was at the battle', remember that there's also Bastion's Keep, where you were congratulated by every other person you saw.To be fair, the Horadrim shown in the [url="http://us.battle.net/d3/en/reaper-of-souls/"]Reaper of Souls cinematic trailer[/url] were brave enough to stand against Death himself, and at least one got away in time to carry out Tyrael's message.
Plus, it's easy seeing these new Horadrim guys aren't exactly masters at combat. They barely last 7 seconds.
Why doesn't Tyreal keep the stone in the heaven? He doesn't want evil to be around the High Heavens but allow them to stay on Sanctuary? Well, that's kind of bias, given that he's already the mortal. He should stand for man instead of angels. Next, I don't know why he always chooses Sanctuary to hide things. It's very unsafe place. He's wisdom, he should know that right? Not to say, stealing and hiding the stone without the help of the Nephalem who defeated the Prime Evil is another mistake.