Yeah, a probe as close as possible to every cylinder would at least tell you something. One probe can be very misleading - I've seen people with blown engines who never saw their EGT's go up. Why? Because they only lost one cylinder, running lean due to an injector problem, but every other one was so happy that the EGT's averaged out to be okey-dokey.
EGT's are also inaccurate over a range - you have to beat on the car to get a range where the EGT's max out at. This doesn't give you nearly enough information to tune. For example, you could be running rich as hell up to 6000RPM, and then starting to run lean. Watching your EGT's will make you fatten up the powerband after a big run, when in reality, you only need to add fuel at a specific point, and actually take fuel out, otherwise. By the reverse, if you're running lean around ~5000RPM, but rich up top, your EGT's may look fine, simply because the probes don't react fast enough.
The other problem with EGT's is that it doesn't seem to be a universal solution. While EGT's may help give you information as to long-term happiness of the setup (running 10:1 A/F with 10,000+ degrees EGT's isn't going to help...
), there are tons of situations where a car with low EGT's is running lean and a car with high EGT's is running rich, and this threshold varies hugely from car to car, probe to probe, mount point to mount point, etc.
To try to make an analogy, using an EGT gauge is like sticking a thermometer in your mouth when you're sick (or the way we tend to mount EGT probes, like taping it to your forehead), while an A/F gauge is like doing blood analysis.
My humble opinion, of course.
And yes, EGT is better than nothing, really. I should mount a probe just for that very basic information, but I'm not really beating on the car that often, so...
I have enough of a hard time trying to find my own virgins for sacrifies, you think I'm going to share?!?!