Right at the beginning when I saw Kettle Corn, I was like: Woah! Bagua calligraphy! ^^
The haiku thing then made it pretty clear that hers is an Asian arts theme. In case you didn't know, circle painting is a very profound practice about reading and getting to know yourself and your interaction with the world and ensuing inner state. I also want to point out that writing a haiku is about more than the 5-7-5 format. Good haikus contain a bit of a turn of expected events or such, surprising the reader in an enlightening-entertaining way. - An example of mine:
On the mountain's peak
Eagles circling beneath me
Sky reaches so deep
The episode touches many angles all worth pondering. Rumble was a bit of a wakeup call for the CMC's 'just doing their thing' and becoming a bit inflexible in their mind that way. Him being driven by own issues and rallying others to seek external affirmation and avoidance is of course another common theme, but in that he also had a teacher role. The CMC were right though that cutie marks have a mind on their own (I would say they're a symptom of the inherent Equestrian magic of the land) and one can always trust them to be a wise guide.
We probably don't have to mention that it was kinda obvious what Rumble's issue was early-on. But as I said, in a way only half of his issue was in lack of understanding (of his older brother) on his part. The other half was in the CMC's lack of realizing what was going on.
This episode's lesson is close to me because I have experienced something like this myself. I once participated in something meant to heal and guide, but the organizers were so used to just doing their thing again and again that they got stuck in a rut and had become a bit inflexible in their mind, going in opposition to what the healing and guidance is supposed to be all about. But that served an important purpose, a little crisis that needed to be experienced by all involved. And that's also the spirit of MLP episodes. Conflict arises as a means to shed light on things that need to be resolved.