I find myself using Blissey P+HB as my most frequent attacker. It's so bulky that with proper dodging it can take out at least 3 Pokemon on average. The down side is that it's very time inefficient. Therefore if you live in a place with many Pokestops I probably wouldn't bother to attack with Blissey. Nevertheless it's the best all around in the game, by far.
Is using Blissey as an attacker underrated? Also some thoughts about Blissey.
I know trainers here love to look for Blissey's best defensive moveset. But I have tried my level 33 Blissey today and used it for attaching a level 10 gym, extremely useful.
The biggest problem with attacking level 10 gym is the first few matches because you only have six to fight against 10. You will have to fight twice or three times if you can't finish all of them at once. That's when Blissey comes in: because it is really bulky, you will have chance to fight off several non-Blissey with it(with dodging of course). Especially when a gym is quite diverse so you can't cover all the type advantages with single mon.
As for defense, Blissey is quite formidable but not necessarily unbeatable. In order to keep the gym longer, other players have to have Blissey too. Besides, i think it is Blissey's bulkiness that makes it scary, not necessarily the moveset.
Here is my two cents after all the gibberish:
1. Power up the Blisseys you got regardless of her moveset. If more trainers have higher CP Blisseys, there will be more in the gym, which will make it harder to take down.
2. Using Blissey for attacking higher level gym, not just defending. Yes, it may take a little long to battle but it surely is better than do it twice in a high level gym.
Answers
The only people underrating Blissey as an attacker are those that take speed into consideration. This site lists Blissey as a tier 1 attacker, along with Dragonite. It is covered here...
https://pokemongo.gamepress.gg/besting-big-7-defenders
"Where's Blissey? Blissey as an attacker had to be excluded from these plots for axial considerations. Her matchups had such high time and power ratings that plotting her would scrunch up all the other species and render them unreadable."
So yes, your observation is correct, and Blissey is really if you have max potions and few revives. I just used my p/dg one tonight and she completely tanks 2 dt Gyarados without dodging charge moves. With dodging she can easily make her way through 4 or 5 pokemon. The question is, how much do you value your time?
It takes longer to take out each individual battle...but can make up that time by making the gym faster to take down.
By getting through the full line up, you get the bonus 1k...meaning 1 less fight you have to do, and most likely a removed defender that you may not have dropped from the gym otherwise - and then it makes it easier to get the bonus 1k for a complete pass next time through too, as you face less defenders.
Getting this bonus 1k a couple of extra times can make up the time difference for each individual battle, and it helps remove defedners faster, snowballing the effect of getting the 1k more often and faster.
People look at a single fight and yes it takes longer, but when you look at the time it takes to drop a full level 10 gym, I have found she can easily make up the time over the long haul.
Not to mention, less time spent healing your line up, and reselecting them before going back into battle.
...and we haven't even touched on prestiging with her.
She is definitley under rated by those that think that a fast gym is measured by each individual fight, rather than looking at the bigger picture.
EDIT ...and she is the best answer to the dodge bug that makes many fights take longer than they need to
Good luck.
While you are at it, if it is a lvl10 gym then just hit the first defender once and remove them - then reset.
This will mean that you only need to attack 9 to get the bonus 1k...and does not increase the number of battles you need to do.
Don't use Blissey for that...take out 10th place as fast as your can
Also, when I do it I usually only take one Blissey in and then the rest are specialist attackers (taking advantage of typing)
As long as 1 Blissey can take out 3 mons in a row, then it evens the odds for the rest of your attackers.
Too many Blissey and you lose the benefit - I use it to almost guarantee the odds of going top to bottom on the gym.
As soon as there is only 6-7 attackers in the line up, then she takes a back seat to the 'right' mons to use in each battle.
I only have one maxed out Blissey at this point and normally use her as intended to defend gyms, but I have found myself sometimes when she is not in a gym using her to destroy high tower gyms, pretty useful for the last 3/4 spots, if you find 3x Dragonite and 1x Tyranitar for example with good dodging you can take the 4 of them, 3 at least, she is truly a beast!
My moveset is P/DG
Blissey is by far the best pokemon in the game. It's not close. She is awesome as an attacker for the very reasons mentioned. The only problem is that she is even better as a defender than as an attacker and seeing as most non-cheaters don't have a line-up of Blisseys, often you would rather have her sitting in a gym earning you coins and dust, than using her as an attacker.
I agree that using a Blissey as an attacker is often underrated, not on the attacker tier list here, but in general discussions among players. I regularly use my maxed out P/HB as attacker. It's usually my first choice against Gyarados and Dragonite, among others. If not in a gym, I always include it as a backup in my lineup for any of my other attackers that may faint due to unexpected issues, such as missed dodges from game lag.
As others have touched on , a P/HB Blissey's strength is retaining the best health in the game. It can make it through more sequential in a row than any other attacker and do more enemy damage per revive (or revive + hyper) than any other attacker. It's weakness is slower battles that other alternatives, although this is often improved significantly if powered up, like most do with defending Blisseys.
For example, I estimate that I can make it through ~7 Gyarados in a row (depends on moveset and level) based on % HP lost with my P/HB Blissey, with each battle taking 30-40 seconds. Alternatively I can make it through ~2 Gyarados in a row with my Jolteon and may get stuck in the dodge/revive loop on the 2nd, with each battle taking 20-25 seconds. Getting through 3x more defenders with no death/revive loop is worth spending an extra 10-15 seconds to me, without hesitation. However, I can also certainly understand how others who are more focused on time would favor Jolteon.