Photoshop CS 5 works in Yosemite. It requires Java 6, which is not included in the Yosemite OS (I migrated from Snow Leopard). After I booted into Yosemite, a message appeared that asked if I wanted to download and install Java 6, which I did. PS CS 5 works fine.

I don't know if this applies to Design and Web Premium but I suspect that it does.

Jon

macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365