Mantis Rider is amazing. It's a lightning bolt every turn that pays for Stoke and needs to be answered. Mana is pretty darn good right now so you can, more often than not, play Mantis Rider turn 3. Neither Phoenix nor Dragon are particularly critical but they're both quality; Phoenix is great if you want to be able to grind out some advantage, Dragon is better for dodging Abzan Charms and Banishing Lights. And finally, Boros Charm would generally be considered a pretty terrible idea, since you'd get DQd. Since it's not standard legal anymore. But if you're not playing standard than sure go ahead, four to the face is pretty good.
EDIT: ALSO, my personal opinion, Hordeling Outburst is always a bad card to play in this deck.