Update 3 (08/09 : 11:00):
The player grift scores now remove the score from solo due to class imbalances. Only 2,3 and 4 group play is taken account for your player grift score. Solo leaderboards are available in the home page or your Grift profile subtab if you wish to compare your GR solo sessions only in the world.
Update 2 (08/08 : 11:21):
As a player, your greater rift scores are added regardless of what class you play in each category - only the best of each solo or grouping is used. However, it still takes a single class to play all Rift categories to represent your clan and clan scoring (so focus on playing one class on all 4 GR categories to represent your clan as champion of that class)
Update 1(07/08 : 19:46):
Rift scoring for all profiles synchronised and ladder positions for GRift scores now up to date (previously, incorrect as some old profiles were using old rift data). The top of the profile also shows a position number for your GRift score - click on it to see yourself in the ladder.
Site has been updated to show scoring based on players playing in all group categories of greater rifts. You'll find a GRift score at the top of your profile; this replaces your best solo position as this score is used to position you against all other players in the site.
New columns are available in the "Players" section to show players by these scores and it is these scores that are used to determine player clan "champions" which is used to score clans as well.
The home page shows the best overall GRifters at the top (in terms of all groups played for one class). If you want to score as high as possible then play your main class in all grift groups - this will rank you higher as well as giving your clan a higher overall score if you are selected as the clan class champion.
How do you tell if you are selected as the clan champion?, simply access your clan details page and the "see ladder" link will break down all your clan heroes by class which will show where you are positioned within that clan.
To see how your GRift scores are added up, you may access the "Grift" subtab in your profile which will show all your Grift achievements as well as their individual scoring.