Taking Kroxa, Titan of Death's Hunger, Claim the Firstborn, Village Rites and Stitcher's Supplier is the right call for a Dreadhorde Arcanist and Arclight Phoenix build in Rakdos. The izzet Arclight Phoenix build plays 16 to 18 draw spells and on average 12 to 14 creatures. regardless of weither we are playig Izzet or Rakdos arclight Leyline of the Void is over kill there simply isnt enough of as reason to play it. not alot of graveyard builds with jund lossig favor and the mirror is a race game one always and the second is always tempo.

In the current build I have put 4 Thrill of Possibility and cut Claim // Fame and added two Ox of Agonas for more draw which is still only 10 sources. Ox of Agonas also does a very good job of getting arould cards like Bloodchief's Thirst and Fatal Push much like Stormwing Entity. Knight of the Ebon Legion takes Stitcher's Supplier  place only can become a real problem ad is a great mana dump at times.

My thoughts on the sideboard are that at the moment it is filled with extra removel ad it just feels off i have started to try ad shape it i a way that it can deal with a bit more but i dont know how I feel about cards like Pharika's Libation, I hasve thought about using  Sedgemoor Witch as another Young Pyromancer to gain life but i think Young Pyromancer is faster and my 3 drops eed to be more powerful but what? Stone rain?

Looks tight, I got absolutely no suggestions without playing a few games. I mean maybe adda couple finale of promise, but just the 2.