As a warrior, should I just use dragon rend to stun the dragon, or should I invest in magic absorption? I could take out a mage with a bow if I needed to. Dragonrend does stun the dragon when it comes to dragon attacks right?

Yes Dragonrend does stun them even when they are about to attack. You can even stunlock them with Dragonrend if you have enough Forify shout enchantments(or all of them you can find).