In a tri-color Tendrils list, wouldn't you just go with the classic Chain of Vapor+Hurkyl's Recall+Rebuild? Aren't those all better than this?
I mean, I can see this being good with Snapcaster, but almost ANYTHING is good with Snapcaster, and I think Snapcaster+Hurkyl's Recall or Nature's Claim would be better. Oath is a more played deck than Tendrils, anyway.
I would agree with you in a TPS shell. In a slower list like Drain Tendrils that takes it's time to build critical mass some point removal is needed. My current list runs Chain of Vapor, Echoing Truth, and Rebuild main and boards into two Hurkyl's Recall. I would probably board one to two of these because of the utility with Snapcaster.
With the addition of Grafdigger's Cage the loss of green is not as backbreaking against Oath as it used to be and you get some additional coverage versus Dredge where Nature's Claim is useless.