Havoc Festival and Spawn of Rix Maadi are both slow and awful. consider 2x Hellhole Flailer and 2x more Spike Jester instead. Crypt Incursion does very little in this deck and Punish the Enemy is just plain bad. consider adding in Lightning Strike . In my experience playing rakdos Exava, Rakdos Blood Witch is almost always the best 4 drop and i would definitely take out Bloodfray Giant for 2 more. Hope this helps and heres my rakdos list- RDW- Rakdos Deck Wins

This looks great mate, reminds me of my first Rakdos deck... Anyway, I don't know about the prowlers helm. Could be replaced with madcap skills or deviant glee, both great cards for this type of deck. Also, as much as I personally love Havoc Festival- people panic when that hits the board- it's maybe not the best choice in this deck. At six mana, it's difficult for you to cast, it could kill you, and it's a wasted draw if it's in your opening hand. Just putting it out there, it's your deck, and I encourage you to play something you enjoy. +1 mate.

Mogis's Marauder for a win con, also fmartel77 that isn't standard legal