SE should make SSS into something like this https://youtu.be/ZXYOVLT1VSs?t=66
This is from a F2P game that I use to play, it's a training room that teaches you the basic of your skills, dodging, etc. Beside that you also have bosses for all dungeons and raid, except the latest raid tier that you can use to practice with. Of course you won't die in there even if you get hit, but it's still a good way to learn to dodge aoe and stuff. At the end of the fight you get a summary of the damage you done, damage from each skill, number of cast etc. If SE can take this and improve upon it for SSS it will be more helpful than hitting a dummy and at the end only tells you that you pass. No other information whatsoever.