never had any problems with light or dark brown sugar, use turbo as my everyday sugar (semi processed sugar) may have seen it as "sugar in the raw" or derivations thereof. Started using that in my blends as it has a much lower moisture content and eliminated "clumping issues".
IF, you are making a blend that you want shelf life from, then I would go with dry herbs, and, grind them to the desired consistency yourself. I use fresh only in compound butters, which I freeze immediately for use later. Obviously fresh herbs have a higher moisture content, you buy them fresh for immediate use, so mixing them to package seems (IMHO & experience) to be a waste, as the main reason you bought them for won't be realized AND your flavor profile/formula won't be the same, see any fresh to dry herb conversion chart. Also there may be health issues, obviously fresh garlic and oil is an issue, (moisture content+enclosed space+heat+time=a science experiment)
The only "fresh herb pac" I've every seen had fresh herbs blanched and frozen, the price point made them more expensive than going to almost ANY market and buying fresh so......................, I'd stay with the dry.
I dry and smoke a good part of most of my own ingredients for Q & QC also it makes them hard or impossible to replicate, unique and yours!
Hmmm, re the last part, is said chicken rub crucial to your formula?, if so, why don't you make CD1978 chicken rub, sell it separately and, use it as an ingredient in your spice blend?
BTW, what specific spice blend are you planning to make?
I have seen Worcestershire, ketchup, chicken/beef/veg bullion etc. (dried and liquid) as an ingredient in some rubs and sauces, however, IMHO, a pre packaged commercially available rub, is in itself a spice blend, so I'd have to say no, I, wouldn't use it.
How would you label it?, "Ingredients, 95% Slappy-the-bait-shop-guys secret chicken rub, and 5% my stuff", just askin.
If you have specific ?'s feel free to send me a PM