In the priority list of:
1. SnB Shield Slam
3. Shield Slam
It's just like that because the SnB Shield Slam is free, and not on the normal "rotation", and the rest of it is going back to the old rotation of 2344.
So, why do most warriors put SnB Shield Slam up top, other then being free? Cuz it's limited time, if timing is right, and proc's happen like they are suppose to, you can get two Shield Slams in the time that would normally be one slam. Otherwise, yeah Revenge is great for that heroic strike, and it does give slighty more burst threat, but think of it SnB proc more of a powerful DoT, or Threat over Time, if you will.
I'm not good with numbers, never have been, I found 2344 on my own just by guessing and stuff, but that's how I see it. *shrug*