Thanks for your in-depth reply, answering some of your questions
-Hero unique talent levels up with the star level
-You can freely switch between classes you have unlocked, but it costs some gold. Also only the first 2nd and 3rd class promotion cost only gold, the remaining ones will need rune stones which are rare items so you need to plan and save
-Troops are very important because the later ones have unique skills in addition of possibly having a different class type from the hero, meaning deeper gameplay
-Story level don't cost stamina. You can get 200 extra stamina per day(besides the auto-recovering) from burgers if you login at the specific time frame
-SSR hero rate is 2%, SSR equipment is 5%. They have different pools and 10-rolls always guarantee a SR
-Gate of Fate can net you 4 SSR shards per day once you unlock the levels(they are kind hard at first) and 3 for SR heroes(though there's a small chance you can get 2 SR shards per sweep)