Not necessarily. With many people such as myself, delidding the chip was the only way I was able to achieve even a moderate overclock with my 4670k. Initially when overclocking to just 4ghz, my chip would hit 90'c with a properly installed corsair h80i (very easy to improperly install these coolers) with plenty of fan power running through it. I even tried it with my 120x38 panaflo U1BX monster. After using the vise method, shaving down the underside lip of the IHS so it actually touched the CPU core, applying CL Liquid metal between them, and reinstalling the cooler i was shocked by the temperature drop. With the exact same 4ghz overclock, my CPU was now hitting a max temp of 50'c, and at 4.4ghz and 1.31v hitting 61'c. And that was using a single 120mm corsair PWM fan that maxes at 2800rpm.
I forget what the micrometer measurements were but there was a clear gap between the CPU core and the underside of teh IHS, only making contact via a glob of intel thermal goop.