Yeah, high precision timers aren't a fix-all. Imagine a loop where you test a single bit of some protected memory. If it takes microseconds to determine the value of that bit that's really bad, but even if it takes milliseconds, seconds, or even hours that's still really bad. This is equivalent to how fast an attacker can download your system's memory during an attack. If that rate is mb/s that's catastrophic, if it's kb/s that's still super bad, if it's bits per day that might be enough to mean that only the highest value systems will be targeted, but that's a far cry from actual security.