The Draconic presence epic destiny ability (tear 1 in Draconic incarnation epic destiny) is not applying the +3 DC to the druid spell Howl of Terror. Ill quote the appropriate parts.
"... and +1[2/3] to your DCs of fear based-spells."
Howl of Terror:
"You utter a terrifying howl, foes around you are paralyzed with fear."