problem is that mods are imbalanced. the when comparing the secondary stats to each other, speed obviously provides a larger benefit than other secondaries.
that's should be the main purpose of 6 and 7 star mods, if they are to introduce them.
if the developers are to address this "issue", then they should increase speed by a small amount for 6 and 7 star mods while increasing the other secondary stats by a large amount e.g. maybe the highest speed secondary being 35 and other secondaries increasing to something like 17-18% protection or offense or something for 7 star mods.
while i don't know what the exact balance for the trade off of each secondary stats will be, this may be in the right direction