Yeh, Yamada was kind of a mixed bag. All in all, I enjoyed it, but I can see why others wouldn't.
And seven deadly sins season 2 started off really slowly, to the point where I actually said to my friend that it was boring me, despite giving season 1 a 10/10 rating. I thought season 2 picked up after the first few episodes though, and I ended up rating it a 10/10 as well; I actually ended up enjoying it more than season 1 and decided to read the manga because I needed more of it.