The latter...using the Disting and other modules to substitute for a relatively simple module such as a noise gen and sample & hold is sort of a waste of the more complex functions they're capable of. That's the real reason for them; leave basic functions to basic modules. Also, the thing about noise is that it comes in a number of different "colors", which are different distributions of noise levels across a given span of spectrum. For example, "blue" noise is weighted more toward higher frequencies, while "red" is heavier on low-end spectral components. When you use these as a source of randomly-distributed signals, these frequency differences translate into different types of behavior by sample & holds, when used as modulation signas, and the like. So while having a noise source is essential, it's also important to be able to control that "colored" distribution factor.
A buffered mult can technically be used for the same function as a passive mult, yes. But they're not the same, so if a given patch function relies on a voltage sag for some of its behavior, a buffered mult won't allow that to occur. And of course in all cases, you cannot mix via a mult -- they only function as one-in, many-out.
Pannable mixer? As of late, I really like Qu-bit's Mixology. It gives you CV over level, pan, AUX send per channel, has an effect send/return, metering, and mute and solo functions, all in 28 hp for $400, which is pretty reasonable as performance mixers go. There are probably cheaper methods, but they'd involve building up a mixer with discrete modules, plus you might not have all of the functionality the Mixology offers for its price.