Just give it time.
Most my beers, even my 1.050 - 1.060 beers take 10 - 14 days for the airlock to slow down to 1 bubble every 5 minutes. I usually don't pop the lid to look for krausen until then.
My Grand Cru is a little higher than yours, 1.078. I'm still getting 1 bubble a minute at day 12. I suspect its going to take close to 3 weeks to finish.
Planning: Agave Witbock, Raisin Beer
Primary: GF Hazelnut Stout
Tertiary: Cranberry-Pom pLambic (est. bottle date: 03/01/08)
Drinking: Cab.Sav/Merlot Wine, Grand Cru, Hazelnut Stout #3, Ordinary Bitter