The last thing you want on an adventure ride is to be hammering single track at breakneck speeds with all of your luggage on the back. This will most certainly leave you stranded at some point, whether it be bike damage or if you come off and break a leg or something. I don't understand the need for such power to weight ratio for travel, at the end of an entire day of riding you may have been 30 minutes or so quicker but with far greater risk and then you'll be so tired the following day you won't be able to concentrate.
Then there's the extra maintenance... if you take it easy your moto will last much longer as screws won't be vibrating lose, wheels won't get damaged (bound to happen if you're going too fast in an area with pot holes), rocks won't be flying into the engine, suspension working full time etc.
Also don't forget the fuel efficiency. Any weight savings and power you gain from a high performance moto will be replaced by the fuel needed to power it for long stretches between destinations. Open up the air intake, derestrict exhaust, change carby jets etc, all these things will have a huge effect on your efficiency. Carrying an extra 10l of fuel is not easy.
Oh and don't forget the initial cost, a DR650 is much cheaper than a KTM690 but after 50,000km the DR will start to look far more attractive... and on the road every day it doesn't take long to hit this.