Previously, Zephrys valued Deathrattles as summoning a minion with stats equal to the difference in stats between the minion's base stats and the expected stats of a vanilla minion at that mana cost.
Now, instead of evaluating it as summoning a minion, it does something more generic, of adding 'that much value' to the opponent's board. In practice, this produces about the same results, except without the occasional card offered to deal with that extra summoned minion (which doesn't exist).
This was pretty hard to explain in a succinct patch note (how many times did you have to reread the above two paragraphs and scratch your head?), so we opted to just say that "something changed with Deathrattles", and leave it to skilled players to retrain their expectations around Deathrattles.
As for why Zephyrs "doesn't like" Silence anymore... I don't believe that anything has changed with Zephrys; rather the use cases that you're using Zephrys in have changed. A really good example of this is Necrium Apothecary. I often get reports of Zephrys not offering Silence for Necrium Apothecary... That's not a bug. That's Zephrys working correctly, with the info he has. From his perspective, he sees a (4) 2/5 that had some Combo/Battlecry, and somehow gained a Deathrattle that it didn't start with. That's a not-particularly-threatening minion, and has some best-guess-probably-not-particularly-threatening Deathrattle. In other words, it's about the same as a Gnomish Inventor that got Soul of the Forest'd. You and I know that that Apothecary is gunna Deathrattle into something much more impactful like a 7/7 or a +3/+3 handbuff, because we know what deck they're playing and what to expect. But Zephrys doesn't know any of that, and so (correctly, from his view) likely doesn't offer Silence.
Chadd Nervigg
I can add some more clarity to that patch note.
Previously, Zephrys valued Deathrattles as summoning a minion with stats equal to the difference in stats between the minion's base stats and the expected stats of a vanilla minion at that mana cost.
Now, instead of evaluating it as summoning a minion, it does something more generic, of adding 'that much value' to the opponent's board. In practice, this produces about the same results, except without the occasional card offered to deal with that extra summoned minion (which doesn't exist).
This was pretty hard to explain in a succinct patch note (how many times did you have to reread the above two paragraphs and scratch your head?), so we opted to just say that "something changed with Deathrattles", and leave it to skilled players to retrain their expectations around Deathrattles.
As for why Zephyrs "doesn't like" Silence anymore... I don't believe that anything has changed with Zephrys; rather the use cases that you're using Zephrys in have changed. A really good example of this is Necrium Apothecary. I often get reports of Zephrys not offering Silence for Necrium Apothecary... That's not a bug. That's Zephrys working correctly, with the info he has. From his perspective, he sees a (4) 2/5 that had some Combo/Battlecry, and somehow gained a Deathrattle that it didn't start with. That's a not-particularly-threatening minion, and has some best-guess-probably-not-particularly-threatening Deathrattle. In other words, it's about the same as a Gnomish Inventor that got Soul of the Forest'd. You and I know that that Apothecary is gunna Deathrattle into something much more impactful like a 7/7 or a +3/+3 handbuff, because we know what deck they're playing and what to expect. But Zephrys doesn't know any of that, and so (correctly, from his view) likely doesn't offer Silence.