I have three notable Phoenix replays in my Lessons Learned files.
https://zero-k.info/Battles/Detail/1907336 in which a sequence of Phoenix runs with Scorcher follow-ups completely collapsed the opposing team's flank in the span of a couple of minutes,
https://zero-k.info/Battles/Detail/1916421 in which a team with a large resource advantage was nonetheless unable to push uphill and end the game for a period of about twenty minutes due to a couple of Phoenixes burning each attempt, and
http://zero-k.info/Battles/Detail/1919898 in which, having learned from the previous, I tried to push a critical mass of Crashers forward with my army but the Crashers all died to Phoenix anyway in part due to poor positioning.
In only the first case did the Phoenixes decide the game; in the other two, their effects were only locally decisive.