Dack is 100% the most relevant red walker and has massive synergy with Chandra's first 0 ability as well as its -3. Getting to a Dack Emblem is a somewhat underrated accomplishment in my opinion. It's hard to judge the continued viability of 4 total pyroblasts in Jeskai in a pre-london mull Meta; the MTGO results are largely Dredge and Brown while SCG top 16 looked largely blue. In the Jeskai mirror, this card is actually pretty good. It comes at opposing narsets/dacks with 2 dudes, Scores you an extra "azcanta" on your narset, gets an unpressured Dack to emblem 2 turns early (without losing the dack, mind you). As a casual aside, this RFG's opposing Bridge From Below's.
In other formats, this and Nicol Bolas, Dragon God could be pretty nuts, you can ultimate Bolas on the third turn after they are both in play.