This particular idea has been abandoned for several reasons.
Tip-jets that put engines on the tips themselves - "hot" tip-jet, unlike "cold" tip-jet where a central turbine sends compressed air through the blades to be ejected at the tip - cause lots of drag, in addition to being very noisy. While the noise problem may have been lessened to an extent by further R&D, the drag problem is more or less unavoidable. This is why hot tip-jets have mostly been abandoned by now.
As an aside, cold tip-jets have been used to reasonable success with the Djinn helicopter: https://en.wikipedia.org/wiki/Sud-Ouest_Djinn
While it has much less autonomy than equivalent helicopters due to lower efficiency, it was also much lighter and much easier to pilot, and enjoyed some commercial success. With a heat exchanger to heat up the outgoing air with turbine heat, a newer helicopter could have had similar autonomy to a conventional one, the slightly lower efficiency being compensated by the lower mass. However designing an adequate heat exchanger would have been considerable R&D work, so no-one seems to have bothered with it as conventional helicopters were already doing the job.
But specifically for tip-ramjets, there is another, even worse problem: ramjets are efficient only above the speed of sound, and propeller blades are very inefficient and immensely noisy when the tip of the blade is supersonic. So you either loose considerable efficiency by having the ramjet operate below optimal speed, or you both loose considerable efficiency and make so much noise that it is physically dangerous for people nearby.
While not a tip-jet or a helicopter, the Thunderscreech showed what happens when you try to use supersonic propellers. It made mechanics literally sick, and could even knock people out from the sheer noise.
The Soviet (and now Russian) Tupolev TU-95 bomber also has propellers that can go slightly supersonic, to get extra thrust at the expense of efficiency when going at max speed, and has been known to be detected by submarines due to the propeller noise.