Looks like I jumped the gun a bit. Temperatures got up to around the same when I ran ATITool for long enough.
Still, it certainly is a better overclocker, if only evidenced by the frequencies detected by the internal test. But I'm going to stick to 500/1000 until I can figure out a way to fix the thermal tape contact with the memory chips. Hard to believe so many cards got out of the factory like this.