Currently, vector objects in Illustrator can be copy/pasted onto Adobe Animate artboards. However, due to how ridiculously slow Illustrator is as soon as you add an image, it's less than ideal for mocking up/storyboarding HTML5 banners/animations.

XD on the other hand is lightning fast when images and vector graphics are used.
If vector artwork such as text and buttons could be copy/pasted between XD and Animate, it would make it the perfect storyboarding program, which Adobe currently doesn't have.