I ran into that my first time against him. Got him on the second try after I changed my party up. I usually ran Verso, Maelle and Lune as my main party and never used Sciel, so I only had a poorly setup Sciel and Monoco for the second half. I had all of Monoco's abilities but hadn't really spent the time setting him up correctly.
I switched Monoco and Maelle around and looked at some Sciel builds for the second try. I never quite got his parry sequence down though, was definitely a slog.
I haven't spent much time on IJ. I'll give it a try at some point though
I play everything with a controller. I believe it's fine on kb+m though. It's a turn based rpg, so while there's timed inputs for attacks and parries/dodges, it's just simple button presses and always the same key and not a 'God of War/Uncharted' mess of QTEs using a dozen buttons.