Since our difficulty adjustment is different than Myriad we have some more protection for this.
I don't see how that follows. It's really the exact same thing but with max adjustments increased 10x. Historically this has led to insane difficulty swings (even at constant hashrates) which can be difficult to distinguish from actual tomfoolery without going in and comparing timestamps. One slight advantage is that -log(max_diff_down)/log(min_diff_up) is 1.94 for Myriad but only 1.5 for DigiByte, meaning the attacker would need a slightly greater share of the hashpower to attack DigiByte. Since DGB has a higher hash rate anyway, a successful attack seems less likely.
BTW I've updated my pull request on github.
We just saw your pull request! Thank you for contributing it! Long story short, we are vulnerable as well to the same attack if our net hash rate falls too low. But we do, however, have some additional protections built in the Myriad does not.
We are going to issue a hard fork in the next few days. We are going to implement some changes to significantly mitigate this problem. In the mean time our chain is moving along fine, but we can use all the hash we can get. It is very likely who ever was behind the Myriad attack will attempt the same with DigiByte. And it does in fact appear that they have already tried / been trying.