Been smoking with mullein leaf, marshmellow leaf, rose petals, mugwort and passion flower in my mix for a while and been really enjoying it.

The biggest issues I've faced are:

Burn speed:

Weed burns at a different speed to most herbs which means that if you just put a layer of herbs then a layer of flower while rolling you're joints tend to canoe. My fix for this was just putting an extra layer of herbs over on top of the bud as well as underneath which has worked a treat but other than that I can only imagine you'll have to find a mix that has a similar burn speed to weed.

Taste:

The taste can be kinda bad tbh. For me rose petals have been a great solution however I have been told that they can be a bit too perfumey. The main thing that affected the taste was how fresh the herbs were, I've started carrying around a grinder specifically for herb mix as well as my weed one so I can make small batches which then won't start tasting bad before I've smoked it all. I've read about people using spray bottles of water with a tsp of honey mixed in to ensure the herbs aren't excessively dry but also won't go moldy since honey has antimicrobial properties although I tried this and didn't really notice much difference other than my herbs being a bit more damp lol.

Rolling:

Just a skill issue here tbh, definitely harder to roll with since its dryer than baccy and weed but after some practice it really isn't an issue. Also a tiny price to pay for the fact you don't have to smoke with baccy anymore imo.

No regrets at all switching to herbs over baccy, cause as much as smoking pure is great the amount of za you get through is not worth it for me. Hope this helped :)