Let me preface this by saying two things.
Firstly, Season 1 of Legion blew me away. It pressed all my buttons with its "retro 60s" vibe, its unreliable narrator and a story that rolled on telling an engrossing story about psychic warfare and possession.
Secondly, this is going to be spoilerific.
So I did enjoy large chunks of S2, but it did have some MAJOR pacing issues. It was (IMO) about 3 episodes too long. They covered a lot of territory, but they could have easily trimmed some of the episodes by a third and fitted it all in a lot smaller space. I get the impression from the number of episodes between S1 and S2 that they may have written for a smaller number, but found themselves having to pad it to meet a deliverable.
Having said that, there was some seriously good stuff in here.
The initial psychic battle between David and the Shadow King, as well as the final war are amazing visualisations of an "impossible" war, and "Behind Blue Eyes" will never be the same for me.
There's also some truly terrifying bits in it. Jemaine Clement and Navid Negahban are beautifully cast and carry off menace so well. Dan Stephens also does well in the scary space.
If you enjoyed Season one, I'd suggest you try Season two. There are some slow episodes in there but there are enough good ones to make it worth sifting.