Title. I see them in the treasure trade, and I take it that they’re specifically for Dragon Trials and High Dragon Trials.
if you’re just starting out and don’t have enough dragons to go around, yes.
Zodiark and Brunhilda are also pure strength, so they’re not even bad.
After that, however, they are worse than the gacha 4* dragons.
You eventually want all dragons for the sunlight ores though.
Same strategy as any 3*. Get at least 1 to get the sunlight (MUB it or nope… as you want) xD because It’s the half of any Unbind.