so why use diglet?
The best 2 Pokemon to use in this case in your party, if going againt Blaine, would be Hitmonlee and Dugtrio. Flareon could be used as a back-up, but stick with non-fire type moves when he is out in battle, like bite, or quick attack. Or whatever moves you have for him that are non-fire.
I say Hitmonlee because he can use double kick and create some real damage. And, maybe I am wrong and thinking of Hitmonchan, he can also use some not-so-expected type moves, like a fire or ice move. Use the Ice one, if possible.
"Do or do not, there is no try" -Yoda
I'm gone...