I tell you my experience. I'm leveling a priest that it's 60 now and since I have also done some instances (and I have full heirloom set with 20% experience gain bonuses) and been very ahead of the guide, I skipped some zones since they were grey quest for me, well it was a real mess. Missing quests because I didn't to the previous to enable the following. Going in a zone then realizing that I couldn't do that quest because I didn't do the starting quest chain, very unconmfortable. In short what I suggest you it's not to skip areas, or make really sure that you do all the quests required (at least) and check carefully the previous zone you'll going to skip to make sure that you won't have problems with struggling finding where to start the quest chain to sync with the guide section.
If you can Solo an instance, you have two options. The first is to take the place apart yourself and sell all the drops on the Auction House. For level 80 characters, Scarlet Monastery, Uldaman, and other mid-level instances are easily soloable, and are a very popular source of cloth and marketable blue and green items. If you're reasonably well-geared, and feeling more adventurous, Scholomance and Stratholme are also soloable, and can be extremely lucrative as a source of auctionable items.
Keep in mind that these quests are optional, and are not necessary to continue leveling and capturing companions. They are also account-wide, so if you complete the quest chain on one character, you will not be able to complete it again on another. However, any progress that you've made will be saved and you can pick up where you left off in the quest chain on another character. The dailies that you've unlocked will also be accessible by all your toons.
I'm just now coming back to WOW and TSM after a long time and boy has this incredible addon changed! Right now I'm leveling all expansion version of inscriptions so I'm able to craft all the illusions. I created an All Herb group from this import ( https://www.tradeskillmaster.com/group-maker/ogth3m9d ) but when I search this group in the shopping tab you see it is searching all items (Scanning x/120 in the status). However, only BFA herbs are shown. I verified that this group is using the default, stock shopping operation and validated that operation was indeed stock. What am I doing wrong?