These temperature reductions are extreme. Intel should have spotted this because the benefits definitely outweigh the cost reductions and negative PR.
That isn't even the main issue with Haswell. The main issue is that there is a lot of variance from chip to chip in terms of voltage required to reach a desired clockspeed - let's say the best 4770k chips can reach 4.6GHz at 1.15V. There are also 4770k chips that can't reach 4.6ghz unless they are 1.35V. That's the thing with Haswell, there is more variance with voltage. By contrast, IVB and SB had less variance in terms of voltage required for desired clockspeeds. So delidding will lower the temperatures, but it doesn't remove the voltage variance which is a side effect (presumably) of the new iVR of Haswell. Once you reach a certain voltage threshold, nothing will make temperatures tenable whether you have a delidded processor or not.
All this being said, Haswell isn't a bad overclocker. Most chips will reach 4.4ghz easily, and that 4.4ghz 4770k will beat a 5.2ghz SB and will also beat a 4.8ghz IVB. Also, asus has tested thousands of chips and something like 70% of them will reach 4.4ghz with nominal voltage - that really isn't bad. The overall clockspeed will be lower but it is still the best purchase for a new system; it just becomes questionable as an upgrade for existing SB or IVB users.
Obviously most users don't consider it a worthwhile upgrade.
Another complication to consider is that stress testing really doesn't work well with Haswell; since Haswell has an iVR it tends to "over" correct the voltage whenever AVX stress testing is used. That means it will add another .1V on top of what your upper most LLC setting is, and that obviously will wreak havoc on temperatures during stress testing. But you won't get anywhere near those temps during real world application use.