I didn't used workshop for two months and I don't know when it exactly happened, but performance dropped down significantly. With less then 1000 parts it slows down like 4000+ before. Funny enought, now HDRI lighting works faster, then basic one.
Materials are much more realistic now but it shall not impact the performance too much. I will probably add settings later to select display quality options. Go in flat lighting mode if you want to have the workshop Rocket fast HDRI lighting is brand new and I spent countless hours optimising it.