Specifically:

The wealthiest 20% of Americans got 43% more healthcare ($1,743 extra per person) than the poorest 20% of Americans, and 23% more care ($1,082 extra per person) than middle-income people in 2012. 

I think the article mentions that the extra healthcare isn't helping and might be hurting?

Yes. So dollar amounts spent don't actually mean much. 

600+ Reddit comments discuss whether the Affordable Care Act is helping:

https://reddit.com/r/science/comments/4ru6v1/a_study_reveals_that_the_gap_in_healthcare/

Sorry, what part of this am I supposed to be surprised by?

That the Affordable Care Act did little to solve the problem:

The trend toward higher copayments and deductibles seems likely to continue under the Affordable Care Act (ACA). A typical individual silver-tier plan sold through the insurance exchanges carries a $2,907 deductible. While the ACA’s Medicaid expansion will boost expenditures for the eight million newly enrolled, they constitute only 13 percent of the poorest quintile, and several states are imposing cost sharing on Medicaid enrollees, which might dampen usage increases.

According to the insurance companies they can't afford to underwrite the ACA any more because poor people are swarming them with years of pent-up demand. So... which is it?

Insurance companies are likely to complain no matter what so they can justify continuing to increase rates every year.