How do I get Divine Orbs?

I have completed over 50 T15 maps, hundreds of high level maps and I have not seen a single one yet. I even have rarity on three pieces of my gear and I make sure to set up towers before doing a juicy map. What am I doing wrong? My build has stalled completely because I can't get Divine Orbs to trade for better gear. Also that's another Issue. In the hundreds of hours of playing I have not gotten a single drop that was better than my traded gear. This is not how these type of games should do progression. It just seems crazy that shit is getting sold for like 50 divine orbs. At this rate it would take me 100,000 hours to get 50 orbs.