My curation ROI is ~19% which is well above the inflation schedule, add another 3% for staking rewards to the mix and I am almost doing a 3x. What i think you are not considering is the ratio of vested hive against the virtual supply. Since not all of the hive is powered up a larger portion of the inflation goes to the stake that is active.
Of course not everyone has the same results but I have been around here for almost 5 years and I know how and when to vote. I don't even need to use a voting bot (only about 20%-25% of my votes are automated).
I anticipate that the next hardork will reduce my curation ROI but I am not sure by how much.