Tobirama didn't really make the Uchiah seem stronger he just explained how and why there power increases so much. Itachi understood it which is the reason he left Sasuke alive to avenge his clan and their reputation. Yes they were powerful and yes they basically destroyed themselves but in the end Senju lasted longer, Hashirama was stronger than their stronger than their strongest Uchiha, and even though Naruto is not a Senju he will end the Manga either with the death of Sasuke or defeat of him. So in the end the Uchiha still loses even though they are very powerful.
So to say that they were so powerful, as they were I am not doubting that but they were controlled and they were destroyed by their own kind. Like Tobirama said it would have happened sooner or later and yes once again just like Hashirama had done someone would have stopped the fighting. Cause after all of that nothing is stonger than the WILL OF FIRE!!!
Even though I said all those misunderstood things about the Uchiha, Itachi to me is on a whole different arena, league, ballpark. I like the guy more as he was more than just an Uchiha and more of a very loyal Shinobi that would do anything for his village and more so for his brother.