While ballista can be problematic, I think fast Ugin (in some decks) is much worse for WB tokens… There is nothing you can do to deal with him once he hits the table.
Also even sideboarding Stony silence does not usually help. It may turn off Oblivion stone and mana artifacts, but it doesn’t get you anywhere closer to your actual goal (beating your opponent with your army of tokens).

I’m not a huge fan of Stony Silence in a sideboard slot since we have such a naturally good matchup against Affinity already. Stony is good against Ballista, Map and Mind Stone, but shutting down their early mana development isn’t nearly as important in a deck that’s really looking to grind. Really, you’re just bringing it in to shut down the Ballista, which is like bringing in Stony vs. Merfolk to shut down Aether Vial. If you need something against Lantern and/or even more insurance against Affinity, I prefer Kataki, War’s Wage. Opponents often board out some amount of single-target removal in games 2 and 3, and having a creature-heavy sideboard to take advantage of that is often the right play.

I’m not saying Ballista is our only problem with the deck, but if you don’t draw your Intangible Virtues in a timely fashion, Ballista starts gunning down your team. It also kills our Auriok Champions for free, can shoot our powerful planeswalkers, which are a big way to pull ahead against the Eldrazi, and fireballs us, since we can go low on life with Blossoms and Thoughtseizes. Of course, there’s still All is Dust and a potential fast Karn to worry about as well, but that used to be more manageable before the advent of Ballista. It may look like a decent matchup on paper, but it’s quite tough.

I faced Death Shadow at GP copenhagen.
After winning a close G1 where i stole his 7 power goyf with my Kari zevs expertise and killed him.

G2 i drop t0 leyline of sanctity then t3 fulminator and T4 blood moon.

It wasent a snapwin but i got there finaly.
He had a hand with like 3/4 discardspells he couldent use.

I get that leyline isent the best always vs DS but i have been really liking it in the board.

^Seconding this, and what about Stony?

I would never have expected the problem to be Walking Ballista. I thought tokens played all the +1/+1 enchantments, or has that fallen off?

My biggest recommendation is to just run abrupt decay or blood moon. People cutting their decays is a huuuuuge reason that shadow is doing so damn well. Even the abzan and jund midrange decks I fight frequently run a single decay.

Thoughtseize rather than inquisition to help mitigate the >3 Cmc issue
And add back in those decays.