you basically handicapped Minato, last I checked raiton armor doesn't actually electrocute anything, saying Minato can't tag him because of that is pure comedy, Minato's seals can move on their own, he doesn't have to make physical contact, he can even leave seals on ppl through rasengan, and KBee pushed A out the way of Minato's kunai, and it was sliced in half.

I guarantee you raikage isn't going to just tank a rasengan, and if A messes with gamabunta for 1 second, it's long enough for Minato to get him, A is not the third raikage, nothing in the manga even implies he could tank a rasengan, furthermore, Minato had wind as an affinity, this means that he may have been able to channel the chakra over his kunai, similar to Asuma, if so, A stands next to no chance, Minato is just a bad matchup for him.