If I have to I would resort to using an image, but I would rather not.
Why? An image is a perfectly valid choice and usually the right one.
There really isn’t any need to complicate matters. Images can be made responsive and it’s not even hard.
An SVG is likely to be your best option if you really want to do this with HTML/CSS so fire up Illustrator and export as an SVG object.
As far as I know, text gradients are supported in SVG but you would have to check.