It is slow, even compared to Daz Studio. If you haven't done so already, adding a M.2 SSD to a system and putting all of Vam on it, including the cache, will make a difference. The M.2 SSDs are faster than regular SATA SSDs.
Also a good idea to flush the whole cache periodically. I do it when it hits 18GB. YMMV. Vam will be very slow to load the first time after a flush, but it will be faster after that, IMO.