My Blissey
Answers
I hope you're right - mine evolved with Pound/Psychic, seems to be the least desirable - however has 15 ATT, 14 DEF and 13 STA, which is about 96-97% CP perfection. I'm going to see how things shake out before committing my 60+ candies - I have an 87% IV waiting Chancey in the wings, but fear it may be forever to get it powered to a reasonable level as they are rarer than Snorlax/Lapras here (didn't even see one during the event, have only hatched..). When I next need a strong defender I'll probly just go for it tho'.
Movesets do really matter - or more precisely charge moves really matter. I have trained and attacked against various Blissies. Those with Dazzling Gleam are the hardest ones. Assuming you are attaking a 3000CP Blissey with your 3000CP Dragonite/Gyarados, if you don't dodge its DG attacks, it will kill you in 2-3 charge moves, if you dodge you will lose much of your precious time to finish it in time. Where as with one bar charge move, you won't lose too much time to dodge.
Move set doesn't necessarily matter when it comes to Blissey, but because Hyper Beam is better than Psychic (STAB and more damage) and Dazzling Gleam is multiple charges (not to mention super effective versus Dragonite) I would rank it under those moves by just a hair. Zen Headbutt and Pound are equally useful imo
there's going to be all the math evidence in the world to rank psychic last of blissey charge moves, but I don't think it'll end up being like earthquake is for snorlax where people will probably advise you not to power up. unlike earthquake, psychic is tricky to dodge. The damage hits early in the animation, and with the slowed moves, its dodge window feels small.
Having a high level ZH/DG blissey and also tested a P/HB Blissey ( see this vid https://youtu.be/v3EtoQuksp4 ), imo, the best defensive Blissey would be P/DG followed closely by ZH/DG.
Pound with STAB will be very similar dmg to ZH, and had the added advantage of being faster, so it charges DG faster, which will deal alot of hurt and time wastage to dodge. ZH is NVE into the high dps psychics like eggy, alakazams, espeons, and also the big tyranitar.
Although ZH is better against her direct counter ( ie Machamps ), but DG is also SE, and is sufficient to deal alot of hurt to machamps, coz one missed DG will knock out dragonite ( see this earlier vid - https://youtu.be/yggO2qncC7U ), and machamp is even less tanky than dragonite.