One change was to Roadhog's hook, making it so that he can't hook people through walls. He's got to keep a clear line of sight of the enemy, because if they make it to cover his hook will fail.
With this change, it looks like Blizzard may have added a whole new problem to Roadhog.
Redditor thefreshyyx uploaded a YouTube video that shows Roadhog taking out heroes, such as Ana, Mei, Reaper, and Zarya in one shot after hooking them.
The problem here is that the hook and scrap gun combo can one-shot heroes that it couldn't before.
This either means Roadhog's primary is too powerful now, or the new hook does too much damage when it lands.
Roadhog with Hook 2.0 can one-shot any 250 hp (or less) heroes.https://t.co/WAz6IKdwCx— Don Ibrahim (@DarkFantasy95) January 6, 2017
Characters like Mei and Reaper could survive the hook and a shot and escape, but now it looks like if you land a hook and land your shot they will be killed instantly.
Then there is Zarya who, at full health, should easily be able to survive this combo.
With these changes Roadhog might not land as many hooks, but when he does there will be many more one-shot deaths.