The problem is more the combination of it with controllers then with Sorgwen. The controllers can attack and then move the golem another square. This way it can happen that 2 controllers allow a golem to move 3 squares away from his summon point and then still attack 2 times via Sorgwen, or the golem covers the controller after the attack. It's really strong but be glad we do not have Rygos in the app - the controller Rygos interaction is also crazy good. Currently I use Khan Queso in this deck (controller interaction) and this is also pretty potent to be honest -> Tacu is just really strong in general.
Etch, Malvolance, Sorgwen + 4 Golems is one of the most anoying decks to play against (I think it's broken but I'm not a good Tacu player)
Rygos (and others) was available in the Beta Testing phase on the app two years ago and no one has bothered to simply make them available?