Yeh, I agree with @ajoslin that it slowly starts to resemble bootstrap's HTML :-) Especially if we want to to add tabs grouping in the future. 

It is a funny story with this tabs directive, I thought that it will be used for simple cases only where people don't want to be bothered writing markup by hand. But now it feels like this is one of the most popular directives lol 
I guess what I'm trying to say here is that we shouldn't make directives syntax more complex / verbose as compared to bootstrap's markup.