The Electric Grand Master can actually be taken out with (electric-resistant) Fighting cards as long as they do more than forty damage
Primal Empathy
Gandalf the White has flash, and grants the same effect to all the player's legendary spells and artifact spells, which is excellent for many Tales of Middle-earth decks
To get some of the best ETB triggers, you should cheat your green cards onto the battlefield with great mono-green cards like Natural Order, Pattern of Rebirth, Kona, Rescue Beastie, or Smuggler's Surprise
Mega Rising offers plenty of value across the board, with high-potential cards being available in the Mega Gyarados, Mega Blaziken, and Mega Altaria booster packs
Another mark against Garruk is even if you do get him to transform quickly, he'll basically be so low on loyalty counters that you'll need to spend several turns making Wolf tokens just to keep him around