My opinion after the patch

[Leviathan-1945]

There is a known issue with the stalling when assets first appear on screen. Blizzard is investigating it.

Game is Lagging!

Hi, Switching to classic graphics will significantly improve FPS and experience in smoothness of the game. It will also significantly reduce load times for you (and the others in the game!). Other people have made tickets for similar issues. Blizzard current suggestion is to life with it or buy a new computer. (Not kidding)