ra/hunter for super armor activation skills, hunter also has a skill that prevents death if it activates and it also has a skill that heals you up if you take more than half of your hp in damage timed attacks also do more damage, If you miss a timed attack you do lose a damage buildup bonus.
ranger/phantom kinda works if you want extra photon points along with rapid casting techniques like the healing and cure technique, attack photon recovery becomes ridiculous if you have either a launcher or a spread needle. You are squishier with no halfline automate or hunters anti ohko skill. You can actually go in battle without carrying monomates if your healing technique is maxed out. Also with the right amount of photon points you can end up reaching about more crit rate than with the other subclasses. But still the amount of damage you can get with this subclass is nominal but it could be better, you still don't suffer as much as you would if you miss a timed attack.
ranger/summoner is strictly for bossing, back in the japanese game, the added defense from the class combination allows ranger to have more staying power point assist also boosts status damage from burn/poison and techniques, non timed attacks, but using it correctly requires a bit of micromanagement. multi target damage does suffer if you choose this class combination. investing in the right skill allows you to gain super armor while using a healing drink with the summoner class, but you also have access to techniques but cast them way slower than a ranger with phantom as a subclass.
Etoille gives added damage to attacks if you time them correctly, it also has ungodly defense which makes it so you don't easily get taken out. You're at the mercy of using monomates at your own discretion with that subclass.