Are people upgrading their armor units and affixing hp affixes? +30 defense is pretty significant and +15 HP can be the difference between getting 1 shot and barely surviving.
If people are really having trouble with the dragon I suggest you get the 3 named Qual de Armor 4* pieces. All start at 13 defense (the equivalent of Primm+5).
Arga can be found in Central Aelio halfway up the western cliff face.
Belta can be found in Western Aelio halfway up one of the rock arches.
Sheza can be found in North Aelio near the bridge under a tree root.
All 3 are in Barrier Red Containers.