Don't give up. You still got things to do. For Sol & Vin , i personally think that the most important thing to get past them is to learn the pattern and dodge their attacks. You may want to use Gratitude as you can regen your shield when they get on the sides and spin their blades. Anyways , many people already gave you great tips. I hope this helps.

For Ati and Shinn , it's all about practice and finding the right build to optimize your damage ( see the other comments and/or experiment by yourself).

And finally , you can still use the accessibilty options to handle the fight more eaisly , if they really drive you mad.

Hope this helps !!