In S22, you just need to farm for 1 other set wearable. e.g. Jade set is wearable by all classes. I had worn a Jade set on a DH for this conquest before.
You can farm the 6th set by asking players to give you a spare set gear during group play (saw on icy-veins).
Or, create a second hero and farm gears by “upgrade from rare”. You don’t really need to level up this hero at all. Then give the set to the main character and GR55 is very doable.