My wife and I are coming to the end of levelling a pair of druids together--1/3 bar from 80. We played dual cat feral from levels 1-77, when I went moonkin/tree dual spec and she went dual cat/bear.
Our experience was different from yours...once we got cat form, we were sold on druids forever. Being a stealth team made finishing many quests insanely fast, and the extra 30% run speed wasn’t bad either. Few mobs would survive us playing shred pong with their aggro for more than a few seconds, and we could handle huge pulls and most elites just having one of us go bear.
Still, if your OH prefers flashy to sneaky, maybe having him go moonkin at 40 would be the best way to satisfy that urge. Caster animations are definitely more spectacular, especially hurricane. Our moonkin/feral teamwork consists of me chain-pulling mobs with moonfire and starfall, and her mangling them to death when they get near me. With two innervates available for the caster, you won’t need to spend much downtime drinking, either.