Potential Blissey Counters
I've performed some calculations and I think I've identified a few Blissey "counters". By counter I mean a mon which can beat Blissey 1-on-1, assuming they are at the same level (not same CP). The calculations are basic, but I simply calculated the highest DPS for most of the mons with a high attack stat, including Alakazam, Dragonite, Gengar, Espeon, Tyranitar, Flareon, Gyarados, Ursaring, Jolteon, Machamp, Primeape and Arcanine.
Long story short, there are four potential counters that I see.
Dragonite with Dragon Tail/Outrage or Dragon Tail/Hurricane.These produce 1148 and 1095 points of damage over an 85 second fight which means that Dragonite should be able to beat Blissey of a slightly higher level than itself even while dodging. Alakazam with Confusion/Futuresight and Psycho Cut/Futuresight.
These produce 1154 and 1098 points of damage over an 85 second fight. However, even with dodging, Alakazam may not last long enough to finish the fight. Espeon with Confusion/Futuresight and Confusion/Psychic
These produce 1111 and 1026 points of damage over an 85 second fight. The issue for Espeon is the same as Alakazam, however, I'm not sure it would last long enough even with dodging. Exeggcutor with Confusion/Solar Beam produces 1043 points of damage in over the 85 second fight. That may provide enough time to dodge, but it will be very close. Flareon with Fire Spin/Overheat
This produces 1092 pints of damage in an 85 second fight. That gives him some room to dodge, but I'm not sure that he'll survive even so. Machamp with Counter/Dynamic Punch and Counter/Close Combat.
These produce 1332 and 1236 points of damage over an 85 second fight. That will allow time for dodging even against a Blissey of a higher level.
TLDR; Machamp is the clear counter, but Dragonite with DT/OH and DT/HC may be a reasonable alternative.
Caveats and notes to the above. The model I used doesn't account for dodging or the attacker fainting early (as I mentioned), so that's its biggest weakness. It accounts for Blissey's defence stat, as well as the attack stat of the attackers, and also accounts for STAB and Effectiveness bonuses for the attacker. That said, I think it can provide some useful insights.
For example, Vaporeon, even with the highest DPS moveset (Water Gun/Hydro Pump), can only produce 853 points of damage in the same timeframe. Not even close to enough given the need to dodge. Similarly, a legacy Snorlax with Lick/Hyper Beam will only produce 724 points of damage to the Blissey (and a legacy Lick/Body Slam only produces 659). Primeape with Counter/Close Combat does surprisingly well, reaching 875 in 85 seconds but it's not going to be high enough to allow for dodging so he won't survive.
I'll likely continue to work on the model, but unless there's another move rebalance, I don't expect any significant changes to the above.
Answers
My RS/SE Rhydon is level 30, CP2804 (IVs 14/13/15 Att/Def/HP). My MS/E version is 2 levels higher with perfect IVs but doesn't do as well. I took down CP2800 Blissey with Dazzling gleam (likely level 32+) with 15 seconds to spare and 40HP left over. You don't dodge fast moves, only the specials. That way you help charge your special by taking damage: going from 164 HP to 64 charges 100 energy so gives the extra use of Stone Edge that wins the battle.
It looks as if the biggest reason why Rhydon does so well against Blissey is because he resists her strongest attacks. Specifically, he resists Pound, which is (generally) much superior to Zen Headbutt in terms of damage and energy production. However, against Rhydon, Pound suffers a damage penalty and that's also true with Hyper Beam making its damage output on par with Dazzling Gleam.
I'll need to improve the model to work in a way to account for Blissey's attacks during the battles.
Thanks again for the input.
Confusion/FS Alakazam is not nimble enough,he needs to have Pc...his ability to dodge is key.
Flareon Fs/Oh is beastly...and WILL do the job.
2400 Flareon took out Chansey up to 2650 on it's own, with a little dancing dodge.
I want Machamp but the 3 I evlved did not get the right movesets.
This is from taking down a very Chansey heavy gym yesterday, solo.
As I mentioned, I believe that Alakazam can't do enough damage while dodging, but the model isn't sophisticated enough to account for that yet.
I believe that, the numbers back it up. I was just unsure about it's ability to survive long enough to take it out. Good to hear that it can do it.
Thanks for the information!
Totoro
Please keep up the good work on this. Blissey is my number one nemises in gyms at the moment and I really want to find an effective counter. Of the attackers you describe, the Exeggcutor with Confusion + Solar Beam is the only one I have, but it is "only" 2369 CP. I have had some success with it and it does work, even for a player with moderate skills (me), but missing a dodge of a Blissey charge move can be fatal. I also have had some success with a Rhydon CP 2678 Rock Smash + Stone Edge. In both cases, it seems like a CP 2400ish Blissey is about the best I can beat. A Blissey with CP 2600 or more will generally time me out or even kill me if I get hit with 2 charge moves.
With 2, 3, and 4 you're hoping Blissey has Zen HB so you have the resistance. Seems like two different answers depending on the quick move.
I had some success with a Psycho Cut / Focus Blast Alakazam against a Headbutt / Hyper Beam Blissey yesterday. Have to dodge the charge moves but can absorb the headbutts.
