It's not that Blissey has excellent defensive move sets it's Blissey has an excellent amount of HP. Snorlax has by far the best defensive charge move the dreaded body slam. It's not Blissey, but it's no slouch either. HB hits really hard even if you dodge it and w/ this dodge bug lol it's a 1 hit KO move for Snorlax.
Poor Snorlax
Ok I write this because I wanna hear your opinion on this.
I feel like niantic hates the big fella! Maybe snorlax has great stats, but he is doomed with terrible moveset!
ZH/BS is the only great moveset and it is legacy (snorlax without body slam, I wonder if that makes sense)
All the other movesets are either mediocre (zh/hb, zh/hs, lick/hb) or terrible (lick/hs, lick/eq)
In comparison, Blissey has superb movesets. Pound is superior to lick, DG is superb defensive move. Actually Blissey doesnt have a bad defesnive moveset and snorlax doesnt have a good defensive moveset anymore!!
I mainly focus on defense because snorlax should be a defensive pokemon. Of course lick/hb is good on offense, but still it could be better. Also, I consider ZH/HB mediocre because everyone dodges HB, many even ZH
Answers
In Gen 1 pogo the panda was one of the most OP mon (if not the most OP). Nothing has a type advantage on it (fighting gets owned by ZH) and no one except dragonite could take him head on. The CP update gave Rhydon a chance, but still he was quite OP.
Now with Gen 2, new mons and moves (most of which are better), the panda got slightly worse in relative terms, but nothing much has changed. It's just that there are many other great options to fight the panda now (Fire spin/OH flareon, future sight espeon etc.)
You are correct though, I do agree they nerfed him when they took away BS, it was the panda's best moveset. It's the only other pokemon that comes close to rivalling a blissey defending power. I'd even argue that the body slam panda is more annoying to fight than a DG Blissey but obviously the DG Blissey will be the better defender overall.
The original poster is way to quick to write off Heavy Slam. While it isn't Body Slam it is still pretty good and comes fairly often. It is also a bit tricky to dodge at first as people likely haven't encountered it all that much and it happens pretty quick.
I have an 89% ZH/HS Snorlax that I hatched that I plan on powering up once I've finished my BS Snorlax. ZH/HS is still pretty good.