Humble Defector is just an interesting card to fool around with, and I don't want to cut a two-mana creature (i.e. I would want to replace it with another two drop). Spikeshot Goblin is super powerful in the equipment deck. With Bonesplitter it becomes Lightning Bolt on a stick, which demands an answer very fast. Trigon is a new addition, I remember it being awesome in SOM limited, as +3/+0 is a pretty dramatic bonus to give at instant speed, making blocks difficult for the opponent. Plus I like some options in the red spell section that aren't "deal damage to target creature or player derp".
That said, I get why you're eyeing those cards, but in my mind each serves a purpose. I really think that I had to cut a four drop there, which still leaves me with Fledgling Dragon as the most reasonable cut. That or I cut Flametongue Kavu, the easy two for one.