You can solo them with any class really with the right items
And this is everything wrong with BG3's combat. The exploits are as obvious as they are abundant. You don't even need items really since they provided that platform you can just Shove them down in various ways from.
The Dragon is the biggest mistake in that encounter though. They couldn't have made an iconic terrifying creature more mundane if they tried. It just sits there like a horse and doesn't burn the party to ashes even if provoked. The dragon rider also acts like an old Bond villain wanting you dead but not actually killing you and leaving instead. I would expect higher quality writing in a modern AAA RPG. The desire to use and show off awesome high level stuff already at low levels is too great here. The dragon rider could have just made a fly-over or left right after killing the Flaming Fist before the party meets them, leaving the party to deal with just the patrol for now.
The dragon could be something terrifying for a low level party to fear and AVOID at all cost, even when they look for a cure in the Creche. Fleeing and diplomacy / deals could very well be an option, to make you feel the progression LATER when you can actually fight one. But instead, it's a horse for now and later (soon probably) you get to fight the dragon. And I'm pretty Larian will provide a "fun" puzzle way for a low level party to kill it. I'd bet on a handy siege weapon nearby or letting a large boulder loose for massive free damage the dragon "won't see coming". Much like the teleporting Spider Queen makes herself
vulnerable to amplified fall damage in her own lair. Because why wait for level appropriate challenges, right?