Maybe I'm just dumb but I feel these sorts of lists fall in the territory of "big number syndrome."
I think it would be easier if we're assuming 252/252/252 spreads we should just use Base Stats.
Ex: Instead of Regirock being 199742 for defense it would be 80 * 200 = 16000. Regirock's SD would be 80 * 100 or 8000.
Now, some might argue this gives an edge to pokemon with higher Base HP, but when push comes to shove, a lot of defense becomes redundant in the upper echelons. There is little difference between Regirock eating Earthquake and Rhyperior eating Earthquake, both of their defense stats are so high already that it actually helps Rhyperior to have more HP.
The major issue with the way you do it is inaccuracy. HP is calculated differently from all stats. Base HP is added to the level of the Pokemon... while Defense and Sp. Def are not. So right there, your list will be far more inaccurate than the way I did it.
Second, running only Max HP EVs on everyone would be unfair to Blissey and other high HP pokemon like Azumarril. Running only max Defense EVs on everyone would be unfair to Cloyster and shuckle.
This is why I explained everything I did step by step. Yes, Deck Knight, the ways you calculate the EVs will change the tier list... However, this list is not made for extreme scrutiny. It really is a made up statistic that (well, I believe) would be most suitable for analysis. It was easy to do, easy to calculate, and could be done en masse to all the pokemon.
Anyway, from a "pure wall" standpoint, you will max out your EVs in both HP and Defense. Perhaps I should make a third and fourth list with 0 EVs which would be more accurate for "sweepers", and then a fifth and sixth for optimal EV spread with the calculated maximum 256EVs invested in defensive points which would be accurate for bulky types like Bulky Gyarados.
I doubt anyone would appreciate the use of these 4 other charts however, and figuring a decent heuristic to balance things out like Cloyster who is among the top in Defense, and among the worst in Special Defense, would be very difficult. Especially to do it automatically. It would be even more convoluted than the current list!
I'd rather stick with the current list as it is. Max HP and Max defense. It is easy to understand, the implications are easy to understand, and there is no fancy AI trying to figure out some optimal spread on a pokemon by pokemon basis that no one would agree to anyway. And yes, it would be an AI, because to find the optimal EV spread that everyone can agree to of a Pokemon is really playing the game intelligently, more intelligently than many RMT users on GameFAQs at least who stick defense EVs into Cloyster and stuff like that :-/
EDIT: I should add, I am willing to do the 0 EV spread, that is a "pure sweeper" EV on all the pokemon. Would that be useful?