Blissey could have never been an Offensive threat. It has a 10 base attack stat and 130 at maximum. You aren't going to be killing anything with that. Blissey's role was meant to be a Bulky Behemoth. But chansey does a much better job then Blissey does. When chansey is holding the eviolite
This item, when attached to a Pokémon that is capable of evolution,
will boost the Pokémon's Defense and Special Defense by 50%
Chansey's defense when holding the eviolite reaches 178(.5) when it has the beneficial nature wich in this case would be Bold
Her Special Defense when holding the eviolite reaches 408 if it is perfectly IV and EV trained. Chansey can still do a lot of damage but with moves such as seismic toss
Seismic toss
> This move does damage equal to the user's level
Counter
The user counters the foe by double the damage it previously received
from it
Thee traits make chansey a much better both defensively as special defensively wall
You can't have 422 for each value. You can only max 508-510 EV train a Pokemon, meaning that if you want to max out your Pokémon's HP and Defense, you would have to train it 252 HP and 252 defense with Bold as the recommended nature
This link directs you to a page with Pokémon that give HP EV
This link directs you to a page with Pokémon that give Defense EV
Hope this helped in a way