Do you have an Obsidian Ring you can wear?
Your Karini is only 70%. The difference between a 70% Karini and an 80% Karini is 50% toughness, an 80% Karini gives you 1.5x more toughness than a 70% Karini. Run it in the cube for max effect until you have a Karini with a better affix roll. It’s kinda tough to get a good one since the affix has such a large range. Because of the way damage reduction works, those last few % points on the affix make a HUGE difference.
Just leave it for now. It’s fine as-is. You don’t have enough paragon/augments to justify rolling the int off, and by the time you do, you should have a source with a higher base damage range. The base range on that one is kind of low, and that’s not a stat you’re able to reroll unfortunately.
For moving past GR100, yeah. You can get away with fewer stacks in lower to mid GRs and T16, but eventually you start needing the extra stacks for DPS.