@Riot, Your Analysis of Fiddlesticks is Right on the Money
The change to Fiddlesticks's Terrify range negatively impacted the player's usability, as you discussed in the patch notes. I don't need to personally understand that as a player, Riot's got the data to prove it for me. The question then is, if you knew this, why did it take you so long to follow up on it? The change was made in 6.9, if you were really following the MYMU then you should have realized this pattern was occurring no later than 6.11...and yet we waited nearly an entire year for you to even mention this interaction again.
I think the main issue I have with Riot's balance team is that they simply choose not to include small changes to champions that they know are needed until they can pair them with more relevant balance changes or until the champion is in the spotlight for being good or bad. This was mentioned with specific regards to Talon's Cutthroat a while back (the change to LeBlanc's Sigil of Malice brought about questions of Talon's Cutthroat and Riot came out and said 'We see Talon's silence as problematic but if we remove it people will ask why are you nerfing Talon he's not even a problem right now'.")
Just balance the game, please. Especially all the little QOL things that would just make the game less frustrating for players like the Terrify range. They may not have a big impact on balance but they definitely have an impact on fun.