I am rather fond of them.
The problem came more with character being as good or better at another's focus and good at everything else and more (due to special splat only abilities. For all the criticism earlier versions of Lunar got for being one note, I found them to be the biggest issue in this regard in my play. Shapeshifting is incredibly versatile, enabling emulation or even out classing of a the stealth, inflitration possibilities of Solar Larceny and Stealth charms. Lunars were also savage (no pun intended) combatant. I ran/observed several combat arena games (not White Room, there were environments to interact with, some had a general plot sort of pen and paper fighting games) and Lunar dominated pretty often being the Champions and Dawns gradually vanished. My Dawn ans Night players felt pretty disheartened. There were some issues with other caste but those stood out most strongly, IMEI wish I had your problem, mostly because I have the problem of not finding an Exalted game lasting enough to experience anything like that. if your concern is balance between the players and not them flaking out before things can really get going, your doing pretty well then. In my experience, people can feel unequal and useless even when they're both playing Solars and having two completely different niches.
I feel like this is due some context: doing so requires a particular build* and then using an Excellency, shapeshifting, or both. It's a neat and useful thing for some Lunars to have in their back pockets, but it I don't regard it as a win button, just a different approach. It's off the topic, so I'm going to spoiler my prattling on that point.These issues appear to have continued through to 3rd, so obviously they're not issues to target fans, perhaps they never run into them. But things like the Lunar build that ends up using 11 dice literally everything and I guess more in what the character focuses on was an indication.
The Aura mechanic struck me as an elegant way of getting to their position. Through careful application and use, Terrestrials can access more power in their native Charmset than they normally could, but it's trickier and not nearly as consistent as a Solar or Lunar's power. I'm not mechanically savvy enough to know how much it narrows the gap, but it certainly serves the presentation: they need to work harder to get the most out of their capabilities.Being Terrestrial means that you in total can't probably achieve the levels of power Celestial Exalted do, but this doesn't close you off from having power, and still being Exalted above mortals. The "floor" is lower, with access often to equivilant effects of the other Exalted in the form of Evocations, Marital Arts Charms without the Terrestrial tag, and so on. But while Solars and Lunars achieve great things with effort, Dragon-Blodoed have to put additional effort to match that. Their highs are not as high, but their feats are still impressive. They also again, get powers that are powerful and outright not something other Exalts do. Dragon-Blooded can call typhoons into war, turn their bodies into living flame, create a turret tree, and fly through the air like Goku in DBZ. These are potent effects that just give them options other Exalts don't have, which means whether it's more pwoerful or not is kind of sketchy a comparison.