It's a lot of things
For starters they printed arguably the strongest neutral card of all-time which happens to work really well in Shaman:
Like seriously that thing is so stupid it makes Zilliax look weak
Then they gave Shaman the strongest Galakrond, alongside the best Galakrond activators and the best Galakrond payoff card. When fully upgraded the Shaman Galakrond reads:
7 mana: Gain 5 armor. Equip a 5/2 weapon. Summon two 8/8 Elementals with Rush.
Like...what the **** man.
Then they gave Shaman this as well:
5 mana summon two 5/6 Taunts....like that just single handedly demolishes 80% of the meta.
It's dumb man