My take on dinos is fairly simple...
Dinos are in every single coral we own. Our corals will expel dinos from time to time as they try to keep a balance within. It's completely natural for them to do so and is very common. When they bleach, its because they have expelled all their dinos or most at least. A lot of corals tend to expel dinos more so when the available nutrients in the tank can't support the dinos within them... so when you have nitrates/phosphates of 0... you are going to have a fair amount of dinos being expelled.
The dinos are often eaten in the wild by various small pods and so forth which is why being protected inside an armored/stinging/slimy coral works well for them... however, when the conditions are right they can proliferate on their own. This is where they come from and why you get outbreaks out of nowhere.
My fight with dinos took a turn for the better after introducing lots of different types of pods. I'm not sure if that was the proximate cause of the dinos downfall but I think it was a primary factor. I did several other things at the time as well though like increasing my nutrients and using h2o2 and doing some blackouts. Don't give up, it's a battle... but you'll win. If you have the time, manual extraction using a siphon daily will help you get this over much faster as well.
Best of luck.