Don't forget that you're coming in as it uses Calm Mind (or an unboosted attack) so it's not like you're switching in one turn and dying the next. Quagsire and Gastrodon are either:Quagsire: 63.2% - 74.4% (2HKO)
Gastrodon: 48.6% - 57.3% (2HKO) only if you roll an average of 53% (considering Leftovers)
Lanturn: 37.7% - 44.4% (not 2HKO but without a reliable recovery move...I don't see lanturn walling Raikou though it can status screw it but on 1 on 1 Raikou will win)
1. going to force Raikou out without taking damage.
2. going to get hit by an unboosted attack, then force Raikou out, allowing you to recover off the damage.
3. take an attack and KO back with Earthquake.
Lanturn isn't really anything new. If Raikou has Sub + an attack other than Thunderbolt / HP Ice then you'll lose. If it's 3 attacks, you can paralyze it before you die. Aura Sphere wont be much different than Extrasensory already is. Obviously, all three are in for a rude awakening if it's running HP Grass.
Aura Sphere is significant against other Raikou counters as well. Registeel and Umbreon are 2HKOd by LO Aura Sphere. Unless I'm missing something, Raikou can now beat any of it's counters with one of the following sets:
Thunderbolt / Aura Sphere / Extrasensory / CM
Thunderbolt / HP Ice-Grass / Substitute / CM
Thunderbolt / CM / Rest / Sleep Talk
Rain Dance / Thunder / Weather Ball / Aura Sphere (Rainly LO Weather Ball OHKO's standard Steelix and Claydol!)
and before I get 1000 replies about how that doesn't make him broken...that's not what I'm saying. In fact, some of them are quite specialized (only RestTalk beats Blissey, only HP Grass beats the Water-Grounds, and the first set is vulnerable to status).