Summary: Having inspiring presence and then equipping high life % and/or vitality gear then casting war cry, battle rage, or threatening shout and then switching your gear back to normal allows the life regeneration (from the life gear) to persist until you recast war cry, battle rage, or threatening shout or until the 1 minute timer ends for inspiring presence.
Example: I have 50,000 life and 0 life per second on my normal gear. I switch my gear to some that gives me 100,000 life and 0 life per second then cast battle rage with inspiring presence as a passive. That gives me 2,000 life per second. I'm then able to switch to my normal gear and my health drops down to the normal 50,000 life, but the 2,000 life per second persists even though it should be 1,000 life per second with my normal gear. You will continue to have 2,000 life per second until 1 minute passes from the time you first cast battle rage or if you recast battle rage, war cry, or threatening shout while in your normal gear.
It's fairly useful in pvp matches since they almost never last 1 minute, but other than that it's just annoying.
I already reported it, but you can enjoy it if they decide not to fix it or until they fix it. Inspiring Presence Snapshot Bug - Forums - Diablo III
Also to be clear I only report exploits that I personally find not any that are posted here before I find them. Not like blizz can't check these forums, but I don't want people to think that I report all exploits from here and then rage at me for ruining their fun.