Honestly, imo the ability is mechanically fine as it is and can provide a greater length of time in which the healer can leave you be than the other two.

The thing is it requires a little more awareness and coordination or else you could end up with a dead tank. Part of this can be simply solved by you as the tank having callout macroed with the ability to let people know you used it and it would also be useful to have a callout macro for when you go into the Walking Dead state.

Really all it needs is better feedback for when you get the Walking Dead state on you, such as an Aura visual effect or something like that to provide visual feedback to the healer and party.