I have this character with my party now, but not sure who to put in reserve, lol... I like having a healer with me for safety, but Reyn is great at taking aggro away from me... might just stick with the party I have for the time being.
I switched my party members a lot and still unlocked all the skills of Shulk, Reyn, Sharla and Dunban easily. Hitting level 99 is easy too (there are normal enemies with level 99). Give all characters a try (except the last one).
In fact I recommend switching out Reyn a good amount of time. It takes a lot of time to unlock his last skill tree because you have to get items from level 90+ enemies for it, so if you stick with him all the time you'll unlock all the skills from his first four trees early and from there until you unlock his fifth you'll be wasting SPs. Even if you put him in reserve you'll be wasting points because characters that don't fight still get a good amount of XP/AP/SP.
Besides, Dunban is very good, and his voice and battle quotes are cooler and way less annoying than Reyn's