I'm really hoping they don't ban Forretress too, as some people are speculating. It's a decent card when not abused, and only now can it be abused by such a stupid game mechanic.
I've been experimenting with Forretress in an Expanded donk deck with Latios-EX on the TCGO AI (Wouldn't be nice to do it on real players v_v ). I find that I can consistently activate the Thorn Tempest Ability at least 7 times on the first turn, 9-10 at the most. Though I often deck out too much after that, and can only do 40-60 Damage alongside it. In other words, it can threaten to donk teams of low-HP pokemon, but not so much big basics, and it can dry out quickly...
However, one thing could scare me: Using Forretress as a Bat alternative for cards like Landorus-EX, Flygon, Even Noivern. Now, this could be quite overpowered if the strategy is used correctly.