Gutretch hangs out on the border between Crystalsong Forest and Zul'Drak. To find him, just fly east from Dalaran until you enter Zul'Drak and Gutretch will one of the be the first NPCs you see.
Gutretch's Pets:
- Blight (Critter)
- Cadavus (Beast)
- Fleshrender (Beast)
One of the best teams to whoop Gutretch's team would include Aquatics, because each of his pets has an undead ability called "Consume," which heals according to how much damage it does. Undead attacks don't hit Aquatics very hard, so those heals won't do much for Gutretch's team.
Alternatively (and this was my strategy), you can use some Mechanical pets to beat the Beasts and use a Beast to beat the Critter:
Build some Turrets, use "Metal Fist" repeatedly, and you'll beat Gutretch's pets with ease! Any way you stack it, this team isn't going to take you more than once to beat (maybe twice if you bring a horrid team of pets to the battle).
What pets did you use to beat Gutretch? Got any tricks for making this easy trainer even easier?