The following information is pertinent to all battle archetypes, so you should read it no matter what:
Waltz III is our most efficient waltz (still) when it comes to HP cured / second. In general, if you're doing a lot of healing in succession, you should be using Waltz III.
If you're attempting to main heal, you'd better have your Anwig Salade agumented with Waltz recast -2 or you should just go home. To be honest, you should really have this augment for DNC if you're serious about it anyway.
Anwig should be used for Waltz III and Healing Waltz. If you're using IV/V, generally you're going for something more potent and not efficiency. As a result, you get to use the +7% potency from Etoile Tiara +2 on those. (A good example of when you might use IV/V as a good choice over III is topping yourself off between Saber Dances while soloing or when your waltz demands are not particularly heavy and you want to minimize damage lost to JA delay. If you're taking damage quickly, Waltz III with recast timer augment is more likely to keep you alive as long as your TP gain rate is fast enough.