Which is why the first line of the response was..
Adamantine stone of change can put +5 Hardness and up to +30 Durability on any level item without affecting the min level or using a valuable augment slot.
Adamantine Ritual I - +5 Hardness and +10 Durability.
Adamantine Ritual II An additional +5 Durability.
Adamantine Ritual III An additional +5 Durability.
Adamantine Ritual IV An additional +5 Durability.
Adamantine Ritual V(Max) An additional +5 Durability.
so my point was if they are going to consider durability stones, they need to be better than the no min level adamantine ritual upgrade and definitely not as high level required
a crafting ritual improvement.. would be preferable...
or even encompass improvements to metalline augments.. such as higher level augments of silver/holy/adamantine/cold iron/..etc.. that add hardness & durability.