hmm well I used ronin in EO1 but I haven't in the sequel so i couldn't help you there. I heard they changed quite a bit however.
protector wise Im going provoke/parry combo at first then anti-whatever skills
b/fguard are good too, but I dunno, not worried yet. anyway I read provoke works 70% of the time at level 5 and 90% at 10/max. but it sucks pretty much at first (10% with one point)
as for gunner i suggest upping guns all the way obviously, then ricochet and wildshot for crowd control
there's the elemental skills if you want too, thats up to you
alchemist all im trying to do is get megido, all else is secondary, although Im focusing on fire so far
medic wise they seem the easiest, im focusing on unlocking salve skills so the basic prereqs for those being cure
then refresh/purify will come it handy
resting only takes 5 levels in this game so its a lot less punishing if you mess up IMO.