Genjutsu its not abot how much raw damage you can deal... Im not a gen user but I always thought that the tags sound nice, that should be more of a strategic kind of fight to compensate the lack of damage. Trying to overpower as a gen user is simply wrong.
Now reading your post I understand it lacks that extra punch that I thought it would have with the tags.
Guess a good solution could be that each genjutsu has a higher % on each individual tag (not just the ammount of tags).
Or even maybe its not underpowered at all and its just harder to use so no one has been using gen properly.. maybe..