Don't forget that Iran scours the world for parts to use for their weapons. Bribing smugglers to send parts to Iran is a known way of compensating for the lack of their own weapons. But importing parts gives the rest of the world the opportunity to sell defective parts. Iran can never be sure that the material they use is the real deal or is tainted. Until and unless Iran is 100% self-sufficient designing and making weapons it is vulnerable.
Death toll from Yemen rebel attack rises to 55 after 10 Saudi troops killed (AP)
from the article: Iran exile group: Explosion of rockets caused deadly blast near Tehran