You. Need. To. Provide. Points. Not. Bullet. Points.
Ferrus. Was. An. Idiot.
There. I said it.
There, I dismissed it.
He was rubbish in solo combat.
He ran off with no support.
He got his head removed by letting anger cloud his judgement.
When you have Vulkan who can do all the smithing that Ferrus does but on a better scale (lol, dragon joke) Ferrus is nothing original or special.
When Angron is angry. Ferrus’s anger is nothing special.
Ferrus was the better smith than Vulkan. He forged Vulkan very own pistol. Manus was also just as stalwart as Mortarion, he could weather the battle just as well. Every Primarch had another Primarch that covered their strengtha in a different way. Manus was a better smith than vulkan, but he workes on intricate details and finesse unmatched.
So he wasnt the best fighter. Guilliman almost got killed by orks. As for anger, Angron was almost killed by being baited by russ. Russ almost lost the VIth in his anger. Truth is that only few primarchs are unique. Why have a stealthy primarch like Alpharius when you had Corax. Why have a assassination primarch like Corax when you had Curze. Their strengths are of different kinds and do overlap. So to say "this primarch has X strength so I dont need this other primarch". Emperor knew some of his creations would be failures and made redundancies.