I would rogue 2 for cunning action definitely; note that elk totem is only good if you are raging, so if you are generating the Spike Growth on your own, you cant do that.  
And yeah I was tired yesterday, should have been X5 for average not X9 (though now I wonder if you can sorceror to enhance that)
I dont use mystic since its UA.  I dont use boons since they are explicitly over level 20.  
And I wouldnt let a dinosaur wear boots, which is why I didnt include it to begin with.  
And now you have more room to barbarian 6 (double carrying capacity with bear totem).  Add enlarge to that and you can double carry capacity again.