Never played an action game before, is this a good place to start...

I’ll have to give a try. Sword Legion completely fell off in use for me in the last bits of Pt Ultimate, because of no i-frames and the tendency to get OHKO’d during the sync attacks. Slow attack seems like it might restore the balance there.

It eases you in pretty nicely, so sure

Slow attack is definitely useful. It's good for crowd control and absolutely decimates single targets. Slow attack blaster is a very good utility tool against some enemies.