Well, the issue is that it's not only Justice that's the problem. As Ozball Justice/Mab interaction makes it so that even if Justice misses her gemspawn once you get your turn there is little you can do because most of your team is frozen.
I am just going to give some anecdotal evidence how balanced and healthy for the meta this team is. In yesterdays GW I have faced:
1st battle: Mab team without Justice
2nd Battle: Justice team without Mab
3rd-5th battle: Valk/Justice/Mab teams with khorvash and kraken filling for each other.
So in 5 battles I have faced Justice 4 times, Mab 4 times, Valk 4 times, Kraken 3 times and Khorvash 2.
I think this problem is only exacerbated by the fact this team is very easy to build (you only need Mab traited and she is the only legendary that you need) so most people use it on defense as it has more than a good chance of getting a win.
I am also disappointed with the fact that the answer to the state of things is to tell us to wait 2-3 months for a fix