I’ve been running Danza on my main yellow stack for a while now, and he’s almost square on advertised percentages. A little over 2/3 of the time I get something really helpful when I fire him…and 1/3 of the time, his tile damage is still decent 
With Leo and Onatel, he actually makes a much better #3 than Chao or Li Xiu, since they basically replicate my already-solid mana control.
The other option would be Wu Kong, but I find he tends to lose marginal boards that were winable, but blows enemies off the board in fights I was already winning. There’s a much broader range of effectiveness for Danza.