You can easily catch a 2k Jynx if you are in a biome with frequent Jynx spawns so you don't need to power one.
The fact that Jynx is a glass cannon shouldn't really matter because the DPS gain and best moveset is significant (compared to the other ice types) to warrant more deaths. The only problem is potion use.
Personally I agree with the site and conclude it doesn't really matter which one of the 4 types you use after Articuno as long as they are 2000CP plus (maybe except piloswine because it doesn't really get there for the wild ones).
Bottom line you shouldn't use the ratings as a clear cut conclusion of their viability.