What you've described is a weaker version of Holmgang. Stay at 1 HP for 6-7 seconds, and then let your healers burst heal you after. The self-healing is going to tend to be superfluous in many cases because you're not mitigating anything if you're not at 1 HP. The same is true for the shield.

If you wanted to go for the 'fight for your life' route, then an alternative approach could be this:

Living Dead: Prevents most attacks from reducing your HP below 1. If you prevent damage this way, this effect is replaced with Walking Dead.
Walking Dead: Renders you impervious to healing spells and most attacks. HP is restored with every attack delivered. Cure potency: X

A variation could be the following:

Living Dead: Prevents most attacks from reducing your HP below 1. If you prevent damage this way, this effect is replaced with Walking Dead.
Walking Dead: Renders you impervious to healing spells and most attacks. Incoming damage is converted into healing. Cure potency: X (Dread Spikes)

The downside to these types of approaches is that you could still be caught out if your invuln extends into a downtime period such as a phase transition or intermission. Another approach that hasn't been explored is to lock the player in to a particular HP total when using their invuln. For example:

Wraithform: Renders you impervious to healing spells and most attacks. Duration: 10 seconds.

or

Bitter Memory: Prevents most attacks from reducing your HP below 1. When the effect expires, your HP total reverts back to the value that it originally was at the point when you activated the ability.