But the thing is pokemons should be different of each other.
Right, Typhlosion is a beast. Also I think Ninetales, Magmortar are really strong (and they don't have protection move).
Empoleon has 2 types, what shouldn't be compared with Blastoise, cus of its one type. As far as I know Empo has Prot, Brine, Magnetic Shock and Metal Sound and Metalic Noise. Blastoise has Brine, Hydropump, Skull Bash, Water Gun and Metalic Noise. Can learn Reflect and Rain for example.
They both are playable, really. As I said post above, Blastoise is good enough for playing.
Decidueye becouse of heal move can not learn any protection move, what is fair.
Swampert is good as well.
Many pokemons are unusable or we just don't see that players use them. People are usually exping popular pokemon (not all players) what is also the reason some pokemon aren't so common. I have really big collection of pokemons, even those less popular and I can make you sure that some of them (less popular) are better than those more popular.