I admit-I'm not the greatest Martyr expert and I barely play it, so I don't really know how the high-end content looks like. However, I do believe that having 36K hp is just plain broken.

 Every grenade pick-up you find gives you 3 charges and every charge stacks 4K hp on top of your hp, so right off the bat you can get yourself 12K hp and then 12K more with each grenade pick-up. That's just silly.

 Maybe high end missions and gear allow you to scoff at such amount of hp, I don't know, but right at the beginning, during low level content-you are unkillable because of it.

 What you're saying does makes sense and, in fact, exactly how I imagine it should work, ideally. Pop Void Shield when you're about to die and then safely activate innoculator to heal yourself up. At least that was how I pictured it to work, until I've tried it and learned I could stack it to no end, with relatively low cooldown.

 So, in reality, when you're a high damage dealer assassin, with 30-40K hp and sniper rifle, you can just tank everything while dishing out insane amounts of damage and not worrying about ever running low on hp.

 I really hope devs will balance it out, either by limiting amount of stacking allowed, or by adding some reaaaally long cooldown on it.