It is crucial to avoid her obliteration damage, as she is immune while doing it, deals plenty of damage and will even heal her if she has saved darkness stacks.
When she has her dragon, you can use your ultimate to execute him if he is below 65% health, so try to save your ultimate when u know imani also has her ultimate up.
If you are playing Stunning Visage, wait for her shield to come up then stun her, which completely shuts down her shield. Then, she is an easy target to burst down.
You can go Unyielding Pressure against Yago, as you gain extra percentage based damage on your dark siphon (650 when in her travel form, 390 when planted).