Scaling on a Tegra 3 is a little weird - 779 for 1 thread, 2093 for 2, and 3709 for 4. Without a lot of knowledge of what's going on, I wonder if it's bouncing the 1 thread between cores? Does the Tegra 3 boost one core and leave the rest at lower clock speeds?
Perhaps it's at least partly because Tegra3 actually has 5 cores and not four. That is, it has 4 full speed cores and one low-speed "companion" core.
This companion core is built using a more energy efficient process but cannot scale to as high frequencies (500MHz). Tegra3 will use this core for lighter loads (presumably like single-threaded activities) transparently to the operating system (which only sees a quad core). 779 is still too high for an A9 CPU at 500MHz but assuming your Tegra3 is switching over to or even bouncing with the full 1.4GHz, then it's within reason.
From looking at this thread, I'd estimate a 1.4GHz A9 (like the Tegra3) should get about 1000 while at 500MHz, the score should be about 360. Thus his 2 threaded score seems just about bang on while the 4 thread version is starting to see diminishing returns.