Tank Hero Pool Advice

I'm kind of all over the place with the heroes I play. I enjoy pretty much all tanks except for Peni, Thing, and, to a much lesser extent, Mag, who I dislike, and Angela, who is by far my favorite. However, I'm looking to condense my pool down to a max of 3 and really start focusing on hero mastery. Does anyone have any advice for a solid, well-rounded her pool?

For reference I'm currently D1 and I'm wanting to make a real push towards Celestial