many people get confused about the main purpose of price feed mechanism.
Let's make it clear:
The present of price feed is NOT to mimic the STEEM/USD price at external market,
but to give a suitable STEEM/USD rate that could help maintaining the SBD-USD 1:1 peg:
The primary concern of Steem feed producers is to maintain a stable one-to-one
conversion between SMD and the U.S. Dollar (USD).
This sentence is not mine, but an excerpt from the White Paper. (page 14).
I think you are interpreting too much into this.
It is impossible "to maintain a stable one-to-one conversion" in the strict sense only by adjusting the price feed and interest rate.
For example, if one reason for the current difference is the 7 day conversion delay in combination with the steem price downtrend, we'd have to adjust the price toward the expected median in 7 days. That median however is computed from the price feed - meaning you have created a price feedback loop. Which is a very bad idea, since loops have to potential to resonate catastrophically and are not easy to control.
The reasonable thing to do is publish a feed price that matches the market rate. The result will be a long-term stable SBD price that oscillates around USD parity.