I agree that in today's world, voltage more than temps is the limiting factor on overclocking. But .... and this is a big but, few would for example run a synthetic stress test long term on a CPU w/ the stock cooler even at stock settings ... temps quickly break 85C and. while that won't damage the CPU short term, most would agree that it is not conducive to longevity. Yes, you certainly can get to 4.6 Ghz with a Hyper 212 cooler .... approximately 1% of CPUs will do that based upon leader board analysis of various sites
while keeping temps at a level (mid 70s) conducive to having the CPU for 3+ years. At 4.6 Ghz / 46 cache . 2400 RAM speed, most Haswell CPUs will hit 1.48v and above.
Here's what Asus recommends:
A very good air cooler is required for voltage levels above 1.15V.
1.20V-1.23V requires use of closed loop water coolers.
At 1.24V-1.275V dual or triple radiator water cooling solutions are advised.
95% of CPUs with a Hyper 212 will do 4.2 to 4.4 while keep temps in the mid 70s under generally used stress testing. 95% of CPUs with a Phanteks will get 4.4 to 4.6 and keep temps in the mid 70s. A lesser % of Noctua DH-15 users will get to 4.7 simply because a smaller % of CPUs will do 4.7 at all, but for those that can, the extra cooling capacity of the Noc (or Cryorig R1) is worth the investment..... A H100i has no value since it can't beat these coolers which cost less.
I am speaking in the context of overclocking for better performance, not to get a higher number so it can be posted on a leader board. You can certainly do several things to get higher overclocks, all of which have a negative effect on performance, longevity or both. For example.
1. Turn off hyperthreading ... reduces heat, hurts performance on apps that use more than 4 cores.
2. Disable adaptive voltage features and run at constant voltage ... wastes energy, decreases longevity
3. Use highest multiplier for just one core ... less performance on other cores
4. Set cache multiplier more than 3 less than CPU multiplier ... hurts performance on certain apps like image editing
The silicon lottery is by far the biggest variable in how far one can OC their system. I have seen Haswell's "1 click OC" to 4.8 on air .... and ones that can't do 4.6 on custom water loops.