Well... okay then. Notes for the less mathematically inclined:
The tier lists are all on the same scale. So you can combine the tier lists as you wish. For example, Regice with 255/255 evs in HP and Sp.D has a lower statistic than Blissey with 0 EVs in HP and Defense.
Erm... Nintendo... wtf with Blissey being so good? Okay, that aside >.>
Overall, the tier list and order remains nearly constant. From a "wall" perspective, the common walls like Blissey, Cresselia and so forth don't take too much of a hit as their EVs are allocated elsewhere. This is especially noting the fact that even with 0 EVs, Blissey is the best Special Wall sitting in tier 129 with a score of 129.01... while Regice with 255/255 HP/SpD spread sits at 128.04. Amazing, and it shows again why the obvious choice for Blissey is to put _everything_ into Defense EVs.
Another note for Blissey is how much (Physical) defense EVs help it out. 120.01 is its 255/255 score, while 111.10 is its 0/0 score. A tier change of ~9 is massive, talking the difference between Dugtrio (108.65) and Salamence (117.23) here.
Another note is that 120.01 (255/255 Blissey) falls under the same tier as 0/0 Tyranitar (120.35). This is perhaps the best test we can set-up for how accurate this tier list really is.
I suggest using Rock Slide/Edge on the two pokemon with the respective EV spreads. Rock, Electric, and Dragon hit T-Tar and Chansey for neutral, so comparing the % lost between the two pokemon will give a very reliable metric of this system. There is a .24 tier difference between them, and that should only be a 2% or 3% difference in % lost....
Actually, let me see Marriland's damage calculator and see what it has to say about that.
Theory Test: Max Attack EV T-Tar with Stone Edge vs 0/0 (HP/Defense) T-Tar and 255/255 Blissey.
Attacker Stats:
367 Attack
100 Base Power (Stone Edge) x STAB
Defender Stats: 0/0 T-Tar
341 HP
256 Defense
"That attack will do between 156 and 184 damage!"
Or about: 45% to 54%
Defender Stats: 252/252 Bold Blissey
714 HP
130 Defense
"That attack will do between 305 and 359 damage!"
42% to 50%
EDIT: Bold 0/0 T-Tar for verification (current 0/0 assumes + nature)
341 HP
281 Defense
"That attack will do between 142 and 168 damage!"
41.6% to 49.2%
Erm... holy ****ing ****. First off, this contradicts the tier list somewhat... but still shows that we are "in the ballpark". I did check-over my code after doing this however, and I found a bug (I forgot to disable the nature of the pokemon). So the 2nd tier lists are going to be edited. Second, that is still pretty darn close to the real value.
Finally... 255/255 Blissey has about the same physical defenses than ****ing 0/0 Tyranitar and comes without the 4x weak to fighting. Goes to show that those defense points _really_ help Blissey out a lot... I mean... a whole ****ing lot.
In-Game testers, I ask for you to verify this experiment please? Or if Marriland's calculator is good enough, just tell me.
EDIT: Okay, edited in the data for Bold T-Tar, which is what the current list gives, and the tier list certainly shows the picture very clearly. Very little damage difference for two pokemon inside the same tier. Granted, Bold 0/0 T-Tar and 255/255 Blissey are only .24 tiers apart.
And finally, apologies for my results being so "dirty", I'm doing this research as I post these messages. So thats that.
EDIT: Okay, a note on the 0/0 charts in comparison with the earlier charts. The "Sweepers" are still all within one tier of each other. However, the change in stats forced a split, as Starmie scored 115.26 while Azelf (the lowest) scored a 14.6. They still score similarly, but the lines are now drawn differently, now smack dab between common sweepers splitting them up.