Should moradin (smithing god and overgod of the dwarves) have metal domain?

I know laduguer and dumathoin have it already (in the dwarven pantheon though laduguer is basically outside it), but given dwarves almost racial LINK to metal/earth etc maybe 3 deities having metal domain isnt so much.

to put it simply: from a canon perspective, no he shouldn't. Craft domain is the only other one he has that we don't have on EfU... so unless the DMs felt like substituting Craft with Metal there would be no reason to give him Metal.

It's not like Dwarven Clerics of Moradin need another boost.

from a canon perspective, thats fine, just seemed unusual given his origins but if the flaw is in the canon information who am I to dispute it.

As for power perspectives, you need to choose metal at the time you GAIN the cleric class so it's unlikely to affect any of these so called 'overpowered' dwarven clerics of moradin you refer to.

There is a difference between Moradin, Dumathoin and Laduguer.

Moradin is prayed to by dwarven smiths. Dumathoin is prayed to by dwarven miners. Laduguer is prayed to by duergar smiths and miners.

Therefore, the domains as it is canon-wise, makes perfect sense.