On my Fury warrior, have Execute selected as a Spell Cooldown option, with both Show Timer and Show Timer Text selected.  Since 8.1, it no longer ever shows Execute as being on CD, even when under 20% (ie. when it doesn't have to rely on a Massacre proc).

Digging into it, this might be a Blizzard issue.  It looks like macros unconditionally try to cast the Arms version of Execute (163201) rather than the Fury version (5308), making Execute impossible to use in macros for Fury, and GetSpellCooldown("Execute") also seems to always return the Arms version's information.  Even GetSpellCooldown(5308) doesn't seem to only sometimes return the properly date (ie. <20%), and at other times return only the GCD length.

Posted by CurseForge user Kaedys | Imported from CurseForge issue #1633 | Raw

Seems fine now

Seems to work for me. Did you check the opacity & color section of the icon and ensure that it's at 100% opacity at both "ready" and "not ready?" By default the "not ready" part will be at 0%

Posted by CurseForge user jadugarr

Ok, dug into it further, because when I logged back in, sure enough, worked fine.  But remembering back to the session where I noticed it, I had swapped to Arms, accepted a queue for warfront and zoned in, then changed my mind and swapped back to Fury.  So the session change had to do with it.

Well, don't actually need to get fancy with it, if you log out and back in as Arms, then when you swap to Fury, Execute retains the spell data for the Arms version, including the lack of CD.  This doesn't just affect TMW, macros that cast Execute will also improperly retain the Arms version.  Reloading UI does not fix it, but session changing or relogging does.

So definitely something on Blizzard's end.  Not sure if that rises to the level of worth coding around or not.

Posted by CurseForge user Kaedys

Here's screenshots of the icon settings, and showing the differing behavior and macro issue.  I've also submitted a bug report to Blizzard about it.

https://imgur.com/a/zXESfwn

Posted by CurseForge user Kaedys

You're not the first person to see this: https://wow.curseforge.com/projects/tellmewhen/issues/1532

However, I was actually able to reproduce it this time. It does require a full logout after changing to arms, which I wasn't doing before - I was only reloading my UI.

You can try deleting your Cache and WTF folders (make sure to make a backup of WTF - that's where your addon settings are stored) and see if that helps, although deleting the WTF folder seems dubious at best to me - that's just what another person with this issue reported.

Because of how broken this is, there isn't much I can do. You can't even track the ID of Fury's execute specifically, which is 280735 - I tried and it doesn't work.

Posted by CurseForge user Cybeloras

FWIW I simply made 2 auras to fix an issue I had with this, one that could only work when spec=arms and one with spec=fury.

This issue with Execute - Fury spec, gets even weirder when you are in the Revendreth Covenant and get Condemn.
Execute used to work OK for me before that, before Shadowlands.
And it was sort of working OK until I acquired Condemn. With the use above 80% and below 20% it seems to have broken the show in the TMW bar properly.
And I do believe Blizzard also has a flaw in it's own actions with regards to the CD of 16 seconds.
Yes, I have it as a Reactive with Check Activation Border and Require Activation Border checked and 2 conditions set for the above 80% and below 20%. I have since dropped the conditions as it didn't seem to matter to Blizzard if they were met.
And to end, it seems there are about 30 Execute and/or Condemn IDs when looking directly.