Supposedly it's been overshooting calculations by a bit lately, so it's not all that accurate right now.
At the moment, the only calculation of Lord Alchemy I found off the top of my head that was wrong was Tyranitar (I haven't checked any other of his calculations, I only checked Tyranitar's because his calculations definitely looked wrong)
252 HP Tyranitar IN SANDSTREAM takes 85.40% - 100.50% from surf from a regular Specs build. Not happening.
Apparently, Metalkid's Calculator is a bit off when calculating the Sandstorm +SpDef to Rock types effect. Instead of checking off Sandstorm, leave Sandstorm's thing unchecked, and instead, give Tyranitar a +1 SpDef Stage since it's essentially the same thing.
With that being said, a 252 HP Tyranitar takes
57.43% - 67.33% from a Modest 252 Special Attack Choice Specs Latios Surf, a definite 2HKO.
While Draco Meteor does
62.87% - 74.01% (
254 - 299 HP damage) with the first hit and
31.93% - 37.62% (
129 - 152 HP damage) after the SpAtk drop on the same Tyranitar. If I'm doing these calculations correctly, that leaves a
32.3529% chance at a 2HKO (so a 67.6471% chance of him surviving) if Leftovers are factored in (Latios has to do 429 HP damage, since 252 HP Tyranitar has 404 HP, and Leftovers recovers (404/16=)25 HP).
Cresselia actually loses here. You switch in, I DD. I hit you, you hit me. I hit you, you die. The only thing that would save you is if you crit, get T-wave hax, or this Mix Latios doesn't have Shadow Ball or Dragon Pulse.
This statement also seems kind of off, since it doesn't look like you're factoring in Leftovers recovery. With Leftovers Recovery, a lot of the time, Cresselia does seem to stand a chance at surviving and 2HKO.