The idea behind the deck is to find a reasonable shell for
Nostrix, Lord of Visions and make a Hooru deck that doesn't just fold to aggro. The drawback of mentor is a huge loss of tempo, but the +3/+3 is a nice payoff. With the exception of Valkyrie Enforcer, every unit in the deck has either Aegis or Endurance. By running more defensive units like Waykeeper and Sentry the deck can better stabilize against aggro. Nostrix on a Shelterwing Rider or Throne Warden makes a nice, hard to remove threat, but dropping it on an Auric Sentry or Kothon is perfectly reasonable if you are under too much pressure.
Edit:
In the next patch, Nostrix will grant +5/+5 and Shelterwing Rider will be buffed to 0/5 base stats, putting it out of reach of Auric Runehammer and making it a much more reasonable midrange card. With the nerf to Bartholo, I think we will see more Time Midrange, and I have changed the removal accordingly. I also streamlined the power base, adding 2 more Cobalt Monuments and removing Eilyn's Favor.