there is a nice guide on party compositions on fextralife:
https://fextralife.com/divinity-original-sin-2-party-combinations-guide-magic-physical-and-mixed/usually in general it's better to go as either full magical, full physical or 2\2. though some builds may go hybrid and geal both damage types. 3\1 tends to be a bit weaker composition. unless you use that "1" as only a buffer. without dealing any damage at all....but even then it's better to specialize him as the rest of the party. just in case.
