In my deck I only use one of each different card, but I have no problem using a Dark Krookodile and a Fighting Krookodile together. They are seperate cards anyway. But if you want to use 3-4 of the same card, go right ahead. Everyone has their own way of building these decks, just like the real thing.
And about that list you sent me...I'll get something together for you soon. Maybe challenge Zach and see which of the three of us can build the better version lol.