I was hitting back and forth between 140 to 180 sometimes. Not all the way smooth traffic and constant speed. In fact heavy traffic in December last year from KL to Singapore. I managed to hit the same as you per tank at 12.5 km/L. That's on full load i.e. 5 adults, 2 kids with luggage. I'm pretty sure if you hit constant 110km/hr, 800km per tank is achievable.

The other Sunday night on LDP from Kelana Jaya to Damansara, sticking to 100km/hr on 6th gear constantly with my family onboard, I manage to get hit 6.4L/100km (15.6 km/L).
For the kind of size and weight SUV, a hybrid engine will only run out of breath.

Turbo diesel is the only economically sound solution for moving big SUVs efficiently.