Yeah, I agree that the Excursion is not all that great -- while the Expedition seems to do battle against the Tahoe/Yukon quite well, it seems like Ford didn't do all of their homework with the Excursion.
While the Super-Duty chassis that it's based on is good for work truck duties, as a family hauler, the Excursion is too bulky and clumsy compared to the Suburban. Even with full-size SUVs, most buyers expect some degree of "carlike" dynamics, and the Excursion is just too "trucky."