The thought behind reservoir is with increasing amounts of decks that are pressing the board this would buy me time and also serve as a win condition over the course of a game whereas something like tendrils typically has a small window for you to play it in to actually win. It also serves as a win condition that can't be Flusterstormed like tendrils. I was able to win 4 of 5 games with it in play throughout the weekend, but typically the wins were via vault/key and if the opponent asked for the win condition i would just show the tezzeret.
Yes, jd nir was my outcome mentor opponent. While i stated that the games came down to whoever had countermagic to hit the big spells his Top was putting in overtime allowing him to find his countermagic in crucial spots. But like i stated in original post, they were back and forth, pretty intense and well played games.
The sideboard is something that I want to toy with more, perhaps getting something like Propaganda in there to slow a creature rush and buy me more time.