Vital Herb

I've been experimenting with vital herb in order to find out exactly how it works. I stand next to the zoologist and kill her pets, then I let my mystic heal me with vital herb.
She is lvl 73, and her vital herb is lvl 6.

Note: I generally tried to ignore the hp regen given by Vital Herb, instead focusing only on its heals.

As far as I can see, vital herb seems to work like Iron Heart. Vital Herb heals once every 3 seconds, not every second like it says in the description. The first tick usually heals about 300-500 hp, the second heals about 600-800, the third heals about 900-1200. After that, it heals somewhere between 900-1500 hp on each tick. While vital herb is out, I keep killing the Zoologist's pets to keep my hp low (so that I can be healed).
I used a stop watch to time how long Vital Herb was out, because at the end of Vital Herb's healing spree, it fades out of existence slowly making it difficult to pinpoint exactly when it stops healing. I noticed that Vital Herb spends about 3 seconds completely frozen (not healing) after it comes out. After those 3 seconds, it starts moving. 3 seconds after it starts moving, the first heal hits my character. I started my stop watch when Vital Herb started moving.
I noticed that after vital herb's 20 seconds of active time, I continue to get healed. The heals continue for a total of 13 heals from the time that Vital Herb starts healing. 7 of those heals happen after Vital Herb's 20 active seconds.

Keep in mind that Vital herb also stays in existence for a little while after the end of the 20 second window (measured by my stop watch). I am assuming that it just takes time to disappear and that it is not actually doing any healing at that point. However, It is possible that it actually keeps casting its heal spell for longer than 20 seconds. The last 3-4 heals happen after Vital Herb has completely gone away though.

So I think it just casts a sort of AOE Iron Heart.

Other Conclusions:

1. Vital Herb's heals can be constantly active. Vital Herb spends 3 seconds frozen before it starts healing, then it spends 20 seconds healing, then those heals continue for 19 seconds afterward. That adds up to 42 seconds, 7 seconds after the end of Vital Herb's 35 second cooldown. That is enough time to cast it again and continue healing.

2. Vital Herb's healing is slow at the beginning, because the "iron heart" has to stack before it reaches full healing ability.

3. Casting Vital Herb without a weapon does not seem to have any noticeable affect on its healing, so the strength of the healing most likely does not depend on the caster's magic attack. It may be a constant amount of healing determined only by the skill's level.

4. Vital Herb is awesome.

Edit: 5. Multiple Vital Herbs do stack. So far, I have only tested with 2 Vital Herbs, but I think more would still stack.

Edit2: 6. Vital Herb can be used with other plants. I often use it with Befuddling Creeper in BH 59. I could have sworn that Healing Herb used to be the one that could be used with other plants.