Wow, that is a big number! However, I remember reading reports that the profiler might not always be accurate when reporting HZB stats, but it’s still worth investigating (this may not be an issue anymore, but read this: Unreal Engine Issues and Bug Tracker (UE-33448))
So, as this is a card game, how are your textures setup? Are they optimised as per my post a couple above this? Are you spawning loads of particles and are the textures for these particles setup efficiently? If you’re performing a lot of occlusion checks against lots of particles, that could go some way to explain this.
You might want to do a bit of research into HZB and MipMapping to help understand where the problems might lie.