Stick a lever near the Dread Guard encounter. Pull the lever, enrage timer drops by 30 seconds. You get a title just for beating them. Remove lever if/when level cap increases.
On top of that idea, what if they did that, but for every boss. And it stacked, so if you pulled it twice, it would double the amount being lowered. With a reset button next to it if it proved too difficult (ex. Pulling it 5 times on NiM DG). That way, a guild can make everything "nightmare worthy"