EXP vs time difference

So I was thinking about this last night, 2 races, both 135 minutes fixed seed. level 21=4 points for both.

Now in my party I was able to achieve lvl 20.90 and solo I was able to get to level 19 after some horrible rng ( no flask no tp, very few white items, had to re-run maps )

What is the point in running with a group if you can just about do the same thing solo?