I'm personally seeing a lot of fire and water ones. I keep refreshing for light. Your friend list can play a part in affecting it too, as your friends can request help and depending on who they often pick chances are you'll see more of that.
Like say if you have a lot of friends with lightning set ups, they'll probably be trying to farm the SR weapons from the lightning raid boss, so it wouldn't be a surprise to see a lot of it on your raid list compared to others.