Just starting out this adventure and am wondering if there's any point in leveling Deekin as rdd?

With the bonuses RDDs get, yes, if you're using him as a melee fighter. If all you're interested in is buffs, then no (although, if memory serves, you can't really control how he buffs you all that well).

Even when you won't be using him as a melee fighter, Deekin can really gain a lot from the RDD bonuses.
Mostly it's to keep him alive and so he can stand up on his own against an enemy.