I agree with
Prime Junta that pure casters feel anemic. In the PotD fights, I cannot tell to what extent, if any, they contribute relative to multi-class or martial class characters.
Yup. When the fights drag on casters become fairly useless -- they don't have that many casts, those casts aren't as impactful as they used to be, and once spent they're sitting there with their thumb up their ass plinking away with whatever weapon they have. Since cross-class martial skills are now gone, they're always going to be pretty bad at that. Martial classes OTOH just keep on truckin'.
-------> multiclass casters are much better, because they have access to their other class's martial skills. With the casting times and risk of interrupt though, even they're better off fighting rather than casting a lot of the time.