Execute is not a an affix found on an affix shard, and it works too, as I have said before, which I have tested, any unique item effect that does not say “you” will work with maniest armor. For example, the unique weapon “Last Laugh” execute proc applies to manifest armor, So far in my testing any unique modifier that says “you” will not apply for manifest armor, but every other unique effect type will. Devs have also stated that in the future, nearly all item affixes pertaining to “you” will be able to be used with it in a future patch. Unique item effects from shields, also apply to ring of shields as well, at normal stat scaling values of 100%. Hope this clears up the confusion on how to properly use The sentinel minions. Forge Weapons works in the same way as well with weapon uniques.
Also “when hit” counts as a you modifier as well, so it wont apply to manifest armor either.