Perhaps not, but then again perhaps so. Arianism is still around us in the JWs and we've got at least one Arian on the RF, although I can't remember who he is... he doesn't run around shouting "OH look I'm an Arian booga-booga-booga" but he's an Arian.
Did Athanasius defend his Christology from Scripture alone?
Pretty much, yeah. It doesn't look like the churches had come to a conclusive dogma about the Deity of Jesus which was why Arius had a sizable number of defenders.
I don't believe Almighty God would have left His elect in the dark about this important truth which was why He included so many references in Scripture to guide those like Athanasius. He had the better Scriptural argument than Arius which is why Christians believe that Jesus is God with us, God incarnate. There IS only one God and if Jesus and the Holy Spirit are God - as Scripture attests - then the Triune nature of God is the only truth.