My math shows an 8.98% increase in your raw FTP or a 10.22% increase in your W/kg. Either way, good work.
Short effort 30/30s workouts are not brutal. They are actually quite friendly in terms of VO2 workouts. They are a good starting point. If you continue the plan, the durations will get longer (e.g., 1min, 2min, 3min) Also, those 30/30s were at 120% making it even more mild. There are other 30/30 workouts in the TR library that are both longer and at higher intensity.
Not every workout needs to smash you to help you improve. With VO2 work, 120% or whatever it might be may feel very different for two riders w/the same FTP. Hence, if you need to adjust it up/down a bit, then do so.
