The Boon of Bloodhunter is over rated (similarly with the Argus one). I have had a double drop, or within or longer than an hour, it varies. However, when you're waiting 1 hour for the next proc and get a single blood, it's disappointing.
To be honest, i don't see the purpose of herbalism for a twink. We spend time and money to expand our gear to be overpowered for the current content and instead use this to fly around picking flowers does not make sense.
I found better locations to farm skinning than dungeons. Dungeons have limited ammount of mobs and the run in run out time is slower than if you server hop from a single location.
When you want bloods, server hop skinning in Stormheim in my opinion. Prolonged Power potions fly off the shelf when you put them up on AH, but it's more of a secondary income. For example 3k Stormscale (20k) vs 20-30 bloods (6-8k)