If you felt like World of Warcraft: Legion hit the random chance button too hard (likely as one of the many players who waited for a random legendary for a spec that never dropped), you will likely be happy to see that recent interviews with Ion Hazzikostas feature the game director admitting that the expansion was too random at the start. The two-part interview is helpfully summarized on Wowhead, and Hazzikostas hopes that the new Azerite armor will alleviate that randomness by dropping in consistent spots. Assuming that it drops there, anyhow.
Hazzikostas also revealed that the Burning of Teldrassil will be available over roughly a week or two, while the Battle for Lordaeron will likely be a bonus for those who purchased Battle for Azeroth a week before release (which certainly does hint at the order in which these events occur).There’s also a bit more detail on splitting up profession leveling between expansions and offering separate skill levels. You can check out the summary, or you can pick through each individual interview.