This is the Kolento Arcane Giant Druid Deck he built and was playing on 
stream. With 20 spells in this deck it’s incredibly easy to reduce the cost of the Arcane Giant massively.
I saw him playing the giant for 0 mana. That’s an 8/8 body for 0 mana, we thought the 7/7 on 4 with 2 overload was a problem with Shaman, well things just got interesting.
Sure, you’re not going to play it on turn 4 for that cost. But with Innervate’s, Raven Idols, and Nourish, you can drop an 8/8 on turn 5-6 fairly often.
I think Druid and Mage are going to be two of the best classes for Arcane Giant. Looks like we will need to tech in some heavy spot removal if it starts becoming a problem!