The problem is that at some point a Pokémon or Fakemon is going to face one whose type makes it weaker or stronger depending on the type or types that each one possesses, and that almost inevitable. The concept of types in Pokemon is based on rock-paper-scissors and it is obvious what needs to be done in those circumstances. In other words, blaming the Pokemon for having a weakness against an adversary with a particular type, when it is the coach is the one that has made good use of the Pokemon and other things in their advantage, it is the responsibility of the coach; not the Pokemon / Fakemon in question.
Anyway, so you can see that I have no problems with this, here is what I think of why it is not bad that it is of the Normal type, in addition to the Dark type. The main reason has to do with this here:
Basically, the STAB gives an increase in the power of the movement that the user executes provided that the type of movement is equal to the user.
Regarding skills for both Rascoon and Roberoon (respectively).
Rascoon: Hustle / Pickpocket
Once Rascoon reaches its final stage, Roberoon:
Roberoon: Technician / Pickpocket
The hidden ability can remain the same, so it does not matter much. Well, what do you think of my ideas?