I do really like the idea of shields without heals. It's one of the reasons why I think WHM is the current best shield healer instead of the normally vaunted SCH.

That said, the other part is the instant cast. .5s is nice and all, but you might as well make it instant if you're going below 1s. It'll also add quite a lot of versatility to a spell that doesn't actually heal.

In addition, adding a shield broken triggered heal is a bad idea. The point of the shield is to prevent the damage, and if you add a shield buff on top of that, then most of the time that nice sized heal will almost all go to overhealing. Completely seperating heals from shields is a better idea I think.

For that matter, there's not really any need to increase the power of the shield as long as the MP cost is brought down a bit. Though making it an oGCD for SCH would be especially nice. Maybe Lustrate could shield instead of heal?