You don’t have to worry that much about Diev’s materials. If is quite easy to farm, thou, I’m haven’t tested it myself. If you are just going to Diev C1, then, you can freely invest more points to Carve. In any case, if you cannot loot the materials, you can always just buy them from the Diev NPC.
The only reason you want to lvl up Cure than 1 is to use it as a damage spell. It is actually quite decent if you have a lot of INT.
As for Krivis, I’m still thinking if I will sacrifice Deiv C2 for this in my build. It is quite worth it, with Daino as the foremost skill I need to get pass the “buff limit”. Zaibas and Zalciai are nice skills as well.