Blissey Strategy

In my opinion there is no such thing as a less than ideal moveset for Blissey since your only worry is the Ivs to stick it in the gym. I would worry about bringing your 2 primary Blisseys above 3k if anything. (Right now your 2 Blisseys act almost like a shield to Gyarados, Dragonite, and Tyranitar in my area. I can only assume about your situation? Is 3k considered a top tier or near the lower parts of the gym? Since you live in a desert biome I assume high IV level Rhydon are abundant.

Other than that most wouldn't advise this but please diversify your portfolio. What if Niantic decides to nerf her? Thats a lot of wasted dust and candies. Please invest in some Dragonites, Tyranitar, and Snorlax (more versatile than Blissey not as great defensively but not a slouch an incredible attacking wise)..

If cp is important in you area, that is something you need to take into consideration. But if you are looking for the best defender, go with one with 15s in stamina and defense, or as close to that as you can get. There is a perfect level 36 one around here and it rolls up wins by itself...it times people out...I literally had to power up a pokemon just to deal with the thing (a ES/SoB Eggy) because it was timing out my kamikaze teams. This particular Blissey has HB, and if you start swiping too early, it will time you out. That would be my advice if you are looking for the best defender.

Don't be a dick and stop ruining everyones fun by putting blisseys in gyms?

I'm also in a desert biome and have a similar Blissey lineup. I stopped powering up about where you did, so I can heal them with a revive + hyper. Being in a desert biome, I occasionally catch Chanseys, so my strategy is to take my time and hold out until I find one that has the potential to reach an excellent CP and is caught at a reasonably high level rather than evolve ones that won't reach as high CP as I 'd like. Note that I didn't say anything about top IV because Chanseys with the potential to reach the highest CP are often not the ones with the highest IV %. For example, a 66.7% IV !5/!5/0 will reach 2945 CP at level 35, while a 93.3% 12/15/15 doesn't have as much potential for a top CP and would reach 2926 at level 35.

Regarding moveset, Blisseys are great with any moveset... far better than any other defender. However, because it is such a good defender, Blissey is one of the few defenders where moveset can make a notable difference to attackers. This makes moveset really matter instead of just having a high CP to hold a good gym postion, like with other mons. If it were me, I'd invest my dust/candy in the best moveset Blisseys, and keep other less ideal moveset Blisseys less powered up. I find it's good to have them at a variety of CP, as there are times I want to be towards the bottom of the tower where it will deter more attackers and help the gym stand longer, instead of going to the top. Having worse movesets towards the bottom of the gym also makes it easier for your teammates to prestige, if it gets knocked to the bottom position..

The only movesets I have powered up to 400 HP are ZH/DG and P/HB. I like the latter because it can double as an attacker (can beat more defenders in row than any other mon in game), as well as a defender, so I use it more often in gyms than other movesets. One could make a case for favoring ZH/HB as well for special situations like gyms with more casual players who don't have Machamp/Tyranitar/Dragonite; players with phone lag; and the players suffering from the dodge bug (it's a lot worse with the latest update).