In the images below show that Holliday 3 can be imbued with Mystic Expansion but not Ballistic Enchantment. The latter of which makes sense. It can also not be imbued with Echo Shard or Mystic Reverb, both of which are consistent with other passives, even though it has a traditional cooldown so Echo Shard should work. 
This post was originally just going to be for the Holliday bug, but I decided to look for more. Calico can imbue Ava with Ballistic Enchantment and Mystic Reverb, both of which appear to do nothing since you cannot damage enemies with Ava melee.
Drifter can Imbue his passive with both Mystic Expansion and Duration extender. I assumed this was a bug but it is not! The range he gains the move speed from and the amount of time it lasts when he leave the range seem to change, I could be wrong on the duration though.
Shiv Ability 3 Bloodletting can be imbued with Ballistic Enchantment and Mystic Reverb. These do not appear to do anything. The ability of course does do damage but they do not activate their effects from the passive damage or the active. I don't play Shiv so if anyone who knows more than me has a correction please comment.
Lastly Silver 4 works the same way as Shiv passive, allowing the same imbuements with no benefit that I saw. I only went through passives or abilities I was curious about but I am guessing many other abilities that are actives that do no damage and have no area allow for Mystic Reverb and Ballistic Enchantment to be imbued. The one that stands out the most to me is Crackshot since I haven't seen another ability that can be imbued by Mystic Expansion that gains no benefit from it. Even Drifter 3 and 4 do even though they do not list their range. I love testing for things like this and will be making more similar posts.
This post was originally just going to be for the Holliday bug, but I decided to look for more. Calico can imbue Ava with Ballistic Enchantment and Mystic Reverb, both of which appear to do nothing since you cannot damage enemies with Ava melee.
Drifter can Imbue his passive with both Mystic Expansion and Duration extender. I assumed this was a bug but it is not! The range he gains the move speed from and the amount of time it lasts when he leave the range seem to change, I could be wrong on the duration though.
Shiv Ability 3 Bloodletting can be imbued with Ballistic Enchantment and Mystic Reverb. These do not appear to do anything. The ability of course does do damage but they do not activate their effects from the passive damage or the active. I don't play Shiv so if anyone who knows more than me has a correction please comment.
Lastly Silver 4 works the same way as Shiv passive, allowing the same imbuements with no benefit that I saw. I only went through passives or abilities I was curious about but I am guessing many other abilities that are actives that do no damage and have no area allow for Mystic Reverb and Ballistic Enchantment to be imbued. The one that stands out the most to me is Crackshot since I haven't seen another ability that can be imbued by Mystic Expansion that gains no benefit from it. Even Drifter 3 and 4 do even though they do not list their range. I love testing for things like this and will be making more similar posts.
