If you had for example might/haste etc and you take Warrior's herb and once it wears off, your buffs are on longer available as well.
I think that's a bug and not intentional..
Edit: Sorry, I thought I was posting in Bug Report, but somehow I ended here. I hope you can move it to Bug Report section, thank you! :)
That's impossible. You had low level buffs then, probably lv1 might and haste then ofc herb = max lvl buffs (patk,atk speed,crit rate) so it basicly overwrites the low lvl buff and when its fading nothing to do
I just tested now and works ok. I had lv3 might,focus,lv2 haste picked warrior herb and it did not even overwrite the original buffs