I self taught the AS Course during Y11 and the first part of Y12 because Chemistry is a passion of mine, and from an AS perspective, Chemistry is as hard as you make it to be, if you're actually consistent with your work, have a genuine passion for Chemistry and an appreciation for the Sciences, the workload will not be as heavy as everyone has exaggerated it to be.
A2 Chemistry however, is much tougher than the AS course, and requires a lot more application, a new load of theory, and flips perspective on everything you've learnt at AS, the thing about A Levels in general that will make the difference between success and failure, especially in the Sciences and Maths, is adaptation, and thinking on your feet, problem solving is an essential part of these A Levels, developing that skill alone will mean once you've learnt theory, and practiced a lot of questions, you will know the style, you will know how to elaborate, and you won't have to ever worry about it again.
I'd suggest taking it if you actually enjoy Chemistry, as people who I know who drop Chemistry because of the 'workload' simply didn't have enough of an appreciation for it, by genuinely enjoying and having a passion for, Chemistry, you will never be in despair about working.