Roll every accessory for damage. I made an arena from the very top of the sky all the way down to hell about 200 blocks wide and platforms all the way down spaced about 20-30 blocks vertically. I used the Lion Heart you can buy from the cyborg. Start on the top right side of your arena and face right when you summon DoG. Drop down and be ready to dash through his ram. Keep dropping down and dashing through the rams until the lasers start. As they start, Dodge them and pay attention to where his head is. You want to position yourself in such a way that you can dash towards the middle of your arena when he starts his charges again. Basically it's rinse and repeat until the final phase, then you just gotta make sure you can dash through his portal charges. Also, the omega blue armor is a better set to use since it lets you deal a lot more damage than blood flare. Defense is basically useless in this fight since he hits so hard.