I have been using my experience with the game so far to try and imagine what a battle with a dragon will look like. As someone with zero experience with 5e or other Larian games, I am likely to be wrong about many of the details, but I suspect the conflict will be brutal. So based only on my 80 hours of game time, here are my thoughts.
The way I see it dragons have six possible ways of attacking: 1) claws 2) bite 3) breath weapon 4) wing buffet 5) tail swipe and 6) spells. I think the typical round will provide the dragon with 2-4 claw attacks, a bite, and an extra action such as tail swipe or wing buffet. Wing buffet will knock all the enemies away from the dragon, where pits will be conveniently placed to provide insta death opportunities. If you try to sneak behind the dragon for advantage, it will use its aoe tail swipe to knock you back, again with pits waiting. Both wing buffet and tail swipe will also knock you prone. Breath weapon will be available every 3-4 rounds and will also set the floor on fire. There is also the possibility it knocks you back and prone. Spells will be primarily used for buffs and defense.
If I am right, these battles are going to be near impossible. I think Larian will provide various environmental elements to help us down it. I envision there being loose boulders that we and hit with fire bolt, which will cause massive damage. Maybe the dragon will be shoveable into a pit.
