The new arena matching makes me pay REALLY harshly for fusing my 2 Takumis. Like, I have him, a solid 4* Raven, a level 35 4* Olivia and a 5* Sharena with whatever Sophia's special is called tacked on (at level 30!!) and the game pits me against monstrosities like Vantage Hector.
Holy cow.
I doubt I can get a full winstreak at this point.
I would think twice before doubling up on ANY unit. I think it's pretty important to have as wide a variety of skills on your team as possible to combat all possible opponents.