Make them give better rewards, add new models to bosses and unique mechanics for each boss. for example
metrica DRM: this boss now becomes gets a bar that can only be broken quickly enough with an asuran console. the player must play a minigame like in eod consoles, where you must imput the correct colours. in 5 man, the boss gets a debuff that stacks up to 5 times. 1 stack for each player that helped interrupt.
Anet, please, DRM's are content that is right there awaiting the potential to be played. Also please make the begining event less of a chore.