Embedding text directly to the images should be avoided in general. When needing to overlay text over an image, the HTML5 banner should be the first choice.
Text amount in banners needs to work in the smallest possible mobile device views, art direction is needed for banners that have a bigger mount of text. Then the image importance is reduced and text importance is highlighted as part of the image needs to be cropped and text moved with art direction, not only scaling.
Scaling can be used from wide desktop to tablet portrait view, art direction is needed for mobile banners at least in the major banners e.g. on start pages, product pages etc.