The main reason you may choose Atraxa over another counters-matter commander is its color identity
Im not listing these because I think we should play them, I just wanted to share my suspicion that Tarkir is the world thats going to get devastated by the Eldrazi at some point to later turn into Zendikar, what with the references to Ugin and the hints at future colorless matters cards in parallel to Eye of Ugin in Worldwake
Iroh makes a ton of sense as an Avatar-Only deck since he works best with Lessons, and nearly all the good Lesson cards are found in the set anyway
With first strike, vigilance, and trample, its clearly raring for a good fight
Although it comes with a relatively high base cost, Hunter's Mark can be used extremely cheaply against opponents playing Blue cards (ignoring their inevitable counter-spells, too), and to potentially devastating effect against Blue planeswalkers it's a tempting sideboard card
Table of Contents show What Are the Lost Caverns of Ixalan Commander Decks