It sounds a bit high for a single power in a single round. Damage for a maximized empowered composite blast should be 12 x 15 + stat mod, let's say 15 or even 30. Halved for deadly earth ticks (although it's applied twice in the first round - on activation and on round finish). About ~100 x2. Though activation should be actually less.
And doing maximized empowered deadly earth costs burn.
Now you can come closer to 500 in a round if you stack both deadly earth and Cloud - a lot of burn if both are maxed.
But actually an AT can do more in 2 rounds. My unoptimized AT at level 17 or 18 was sometimes doing 270 aoe damage per spell. He can cast 2 such spells in 2 rounds, plus 2 more quickened weaker ones.
Yeah, Kineticist powers last many rounds... But really, what enemies survive more then 2 - 3 rounds?
More importantly, AT attacks are often party friendly or can be aimed not to hurt allies.
But once a Kin conjures a death zone, the rest of the party better stay the fuck out. Fine if you solo, I guess.
Bruv, you're missing the point. Is it 150 or 500 damage per round? Who gives a fuck, with both of those numbers there is no single enemy in the game that can last a total of 3 rounds against it*, including the Lantern Cuck. "You'll damage your own party" - no you fucking won't, this ain't Baldur's Gate, you have a very clear, distinct, easily marked AoE and all you have to do is make sure your party members don't step into it.
This is an ability that you really cannot defend against. There's no AC to make sure you avoid it, it does not allow any Saves and all you can do is reduce its per-round damage by.... what, 10-20 points per round, against well over 150?
tl;dr - Post-Level 13 having a Kineticist with Deadly Earth in the party pretty much makes having any offense-oriented characters completely obsolete, as they will never, ever be able to compete. It only gets worse once your Kineticist gets Cloud, because now he has
double the original offense, i.e. twice the offense that no other build can compete against.
*Specters might, depending on the composition of your Composite Blast, but Specters are encountered in a grand total of 2 places in the entire game and are almost completely negated by Death Ward, so it's hardly a drawback