Which 5 star should i switch out in World Tree?

So, I have finally started getting some five star heroes, thanks to this world tree event. I just started playing about 2 weeks ago.

I have Exorcist and Dwarf Marksman the highest. Last night, I got Beastmaster. And just right now, I pulled Purgatory Golem. From here, at the end of 30 days, I'll have Spider Queen, and I'm going to start saving for Abyss Lord in the Burning Crusade, since he seems to be the best on to go for in there, according to the tier list.

So now I want to start looking to my next stratagems. I have enough leaves for World Tree to do one trade. Since this is my first 30 days, I'll get Spider Queen at the end of it. Should I wait and reroll her, or would it be better to reroll Beastmaster or Purgatory Golem? I really like both of their skills, so far, but it seems like Purgatory Golem is the better front line warrior of the two.

Thoughts and suggestions welcome.