How does the 3 second delay on Koumei's Omamori function?

[(PSN)Unstar]

I feel like I've got to be misunderstanding something, and I've had trouble finding explicit information on exactly how Koumei's 3 works.

If you've got a charm, then when you get hit by an attack it has a 50% chance to heal you instead of hurt you.  Regardless of the result of this "coin flip", one charm is removed.  Okay, I'm following so far.

But then there's a 3 second cooldown until another charm can be used, and I find that really confusing...because a Warframe can get hit by a dozen different things in the course of 3 seconds.  Are hits received during this cooldown period in any way impacted by the previous "coin flip"?  Or does Koumei just take them all?

I'm trying to understand this ability better, because on paper (from reading both the wiki and in-game) it seems like for 1 nanosecond every 3 seconds, this ability might protect you.  And that doesn't seem like much, so it makes me feel like surely I must be missing something.

[(XBOX)elementXGHILLIE]

No sounds like you get it to me, it's not great.

It's far from a main survival tool, but it combos decently with shield gating and rolling guard. 

I run it on Vauban and like it more there than on Koumei. Vauban gets Shield from bastille, so this makes that last longer, and when he doesn't have shield he defaults to shieldgating with his low base shield, he also has substantially more CC than Koumei.

[L3512]

Koumei has a lot of unnecessary restrictions, it's like all four abilities are underdeveloped so you end up with an interesting but mostly flawed frame.