Are you likely to face CR 6 creatures at character level 16 very often?
See, that was their (WotC's) first mistake - basing it on HD and not CR. HD vary widely with a single CR, let alone a range of CRs (such as those a cleric would encounter with his party). The CR-based system works, even at epic levels (assuming, of course, that the CRs are accurate

).
(Incidentally, the second one they made was 2d6 HD of undead affected, instead of 2d6 undead affected.)
No, I didn’t think so. You’re more likely to face four Colossal Zombies (A CR 16 encounter). A single Colossal Zombie has forty-eight hit dice.
Huh? The only colossal creatures I could find in the MM are very old dragons, and they have a bit more than 48 HD when zombified - red and silver dragons have 80 (~CR 26), and golds have 81 (~CR 27). Four of them would be an EL 15 - he was right on that point - but when is a party ever going to face four colossal undead dragons?
Therefore, I’d consider Turn Undead to be a 30-foot spread (it is currently a burst) that forces all undead in its area to make a Fortitude saving throw against a DC of 10 + ½ the cleric’s level + the cleric’s Charisma modifier.
Since undead have a low Fort save, that might actually work. It doesn't really make any sense, though, unless it's inlficting damage. You're channeling holy power to scare them with the might of your deity (i.e., turning) or cow them into submission (i.e, rebuking). That's a Will save.
I'm curious to see if he's actually tested this "Fort save" system, and whether or not it works. Personally, a far easier fix might be to keep the Will save vs. turning and give undead a high Fort save to offset their lack of a Con score. Undead are notoriously hard to kill anyway, whereas there's no real justification for their high Will save (barring mindless undead, which are immune to mind-affecting effects anyway).
It just gets worse when we go to Epic Levels. Let’s look at the Atropal, which has 66 hit dice (at CR 30). Yeah, that’s right, you can’t turn this thing until level 58 at least. Demiliches are immune to turning outright. Hunefer are a 50-hit dice undead with a CR of 25 (so that’s level 42 before you can even try to turn it). The Lavawight is a bit more acceptable – it’s only got 32 hit dice compared to its CR of 23.
If you mean the broken mechanics, then yes. An atropal should be CR 71; hunefer CR 49; and lavawight CR 39. But I got those from UK, so you can't fault the guy for not knowing
You realize that actually took up more time and space than the actual turn undead rules right?
*snort* I ramble, but even I get to the point faster than that.
Seems about right to me. . .what's the problem? You want characters to be able to turn colossal and gargantuan creatures easily?
No, but these are zombies we're talking about - they're not very bright, nor very strong (force of will-wise).
As far as I'm concerned, the cleric in a 16th level party should have to be lucky to turn a CR 16 undead creature meant to take on the party by itself.
He meant
EL 16, not CR - there are four of them. A cleric should have a 50% chance of turning an undead of equal level.