Sorry, but my searches did not find the answer.
How do I go about getting more than 28 devotion points with a character? I have finished the main quest line and have the existing shrines. I got the message that I can play at the next higher difficulty.
Thanks!
Because the shrine on normal and higher difficulty are not the same 
http://www.grimdawn.com/forums/showthread.php?t=26777
Total Shrines: 59
Normal: 28
Elite: 17
Ultimate: 14
You need to complete the main quest again on Elite to find 17 points and complete again again on Ultimate to find the 5 missing points
The post above me answered things perfectly. Just so you know, Veteran and Normal are the same thing when it comes down to shrine hunting. So don’t bother with Veteran. Also don’t be apprehensive to enter Elite, it’s never that hard. Ultimate however is a gear check
At the character select screen, change the difficulty from “Normal” or “Veteran”, to Elite, then start the game. This will put you back in Devil’s Crossing and allow you to play through the game content again at a harder level, including all quests and most of the shrines. You want to play Elite from roughly level 50-70, and then Ultimate is intended for level 70-85.
If you don’t get any devotions in the Crucible and you get all possible devotions in Normal and Elite, you’ll end Elite with 45 devotion points and need to get just 5 more in Ultimate to cap out.