Dishonored 2 is a rare sequel - in a lot of ways it improves upon the first installment, but in a lot of other ways it's a disappointment.
Having two protagonists is certainly an improvement, and each of them having very different power sets makes sense both in-universe and in a gameplay sense. Both Emily and Convo are interesting protagonists and their powers can make for somewhat different playthroughs.
The problem mostly stems from the lack of interesting missions or characters. The entire narrative is driven by revenge, which is fine, but I never felt as "connected" to the story as I did with Dishonored 1.
Locations in Dishonored 2 are far more interesting, however, with the Addermire Institute and The Clockwork Mansion being particular standouts.
The world-building in Dishonored 2, like Dishonored, is just astonishing. Karnaca feels like a lived-in place, and the in-game lore does a great job of hinting at the larger world of Dishonored and setting up many future installments...though after the lackluster sales of Death of the Outsider, it's unlikely we'll get to see them.
All in all I recommend Dishonored 2 for any fan of the original. It's well worth a play through or two.