Storm's blades are slightly smaller because storm needs them least. Storm gear has the highest attack boost of any school. Storm spells also have the highest base damage of any school. Storm also has more blades than most other schools. Supercharge is an extremely powerful blade that only storm has. The last thing storm needs is a stronger blade.
Storm blade was not meant to be 35% because it will be crazy for all the schools. It also was not made to be 35% because storm would have too much power into it. Storm Owl at least damage+blades and traps:(1525+35%+25%+70%/feint=Over 4000 damage)