You can't stack enchantments. You were only working with 25% better improving.
It's obvious you don't know what you're talking about.
Go and try to improve something with a 25% fortify smithing gear. Then try again with two 25% fortify smithing pieces of gear. Then come back and say that again.
I have both of these at 100 so I decided to find out. I got 4 armour pieces of 25% better of improving and smithed and upgrade a Daedric bow to 84 damage. I don't get the thing here, that is high damage but not in the 300 zone. Alchemy is what causes this then. Without potions smithing and enchanting are balanced out.
Do you have the Daedric Smithing perk? All 5 levels of the Overdraw (Archery) perk? Archery skill at 100?