- Monster hit dice. While having a stated "expected" hit point value for monster is good for the time pressed, having a hit point range lets the DM toughen or weaken opposition without having to scale other combat numbers. For ex, if the PCs tend to deal "more damage than normal", the DM can scale monster hit points upwards. In games where combat is de-phasized or the DM just wants to make a fight easier or quiker, hit points could be swung to the lower end. Also, minibosses or "tough guy" foes can be created by tweaking only HP.
Random monster and by extension player HD is sort of a mixed bag, on large groups of similar enemies, such as kobolds, gnolls, ect... it's fine, it adds a useful sense of variety. For larger "solo" type enemies, random hit dice doesn't really do anything other than make a fighter shorter or longer. If you want a serious level of randomness to a powerful fight, make the range of damage more variable. An enemy can dish out 25...or 100 damage, who knows?
I adjust most of my creatures HP on the fly in 4e games depending on how long a fight is taking vs how long I want it to take. Generally speaking I like my fights to be "spikey" with high damage and low HP and lots of enemies.
I wouldn't want this to be random though, because even though I already generate the numbers at the table, I don't like having to have a fixed range. If I want the HP to be 50, it's 50. If I want it to be 10, it's 10, the battle is exactly as fast or as slow as I want, I'm not limited to rolling 5d10 to get each HP number for my enemies, when there's a lot of them, this is also especially time consuming.
- Magic Item cost. In a world where magic items are individially crafted objects and not created from boilerplate post-industrial templates, each item should have a fairly unique value (based on materials, craftmanship and the general eccentriccies of magic). Also, again where time-pressed DMs might just use the average value, a generous DM could use variable pricing to reward a PC with an on-the-cheap magic item, and a RBDM can jack prices up to the max.
I don't think there's a real good way to simulate this through rules. There might be some useful guidelines that some merchants are price-gougers and some merchants are generous, but I don't think there's any real effective way to randomly generate these numbers without really becoming a waste of time.
- Treasure generation. Tying in with the above, variable hoard sizes and content allow the DM to customize treasure distribution in both value and content. Again, DMs could take the average, but the presence of a range and possibility of random generation allows for tweaking rewards within an acceptable range.
Again, I'm not really sure how beneficial this is to the game. Sure, it feels a little bit more natural, but as a long-time WoW player, RNG is one of the most annoying things on a boss fight. We all contribute, we all work hard, yet, only some of us get rewarded. Sometimes it can feel very, very unrewarding to have put in hours and hours and really get nothing in the end. Sure, some people are really big on the "experience" of the game, and that is indeed important, but given that hoards are well
hoards, I think it's quite realistic that every player should be able to get something out of it.
I like to reward my players for a job well done, so even if I
don't have the random treasure reward them with something useful, there will be some king or baron that will make up for it. Certainly not every treasure hoard will reward everyone, in fact in my games very very few will contain anything other than a pittance.
I don't feel random generation really benefits anyone here. Generally speaking it takes more time to look up a randomly generated item than it does to just pick one or say it's a "+1 item of your choice". I'm not here to build my players characters for them.
- Mundane items. This will likely be the most contraversial, as it hasn't been done before. D&D has always used a fixed price for the majority of equipment tables - and this really makes sense for initial character generation, but I'd like to see a variable range on prices for most items (at least anything worth a gp or more). It would make sense to use the average price when genrating PCs, again, having the variable prices built into the tables would give the DM a tool for those times when he may want to introduce some random (or semi-random) fluctuations to emulate some sort of economic fluctuation.
Simulating economics in a D&D session is I think, rather contrived. Sell high if you want your players to have a lot of gold or you expect to make them spend a lot of it. Sell low if you want your players to be poor, mix in a few merchants who may give better or worse deals than others sure. But attempting to adjust the prices of longswords because the grain fields of Edoras were burned by rampaging hordes, thus reducing supplies to some country which mines ore for sword production in some other nation is really silly.
I honestly don't appreciate randomness in rules. It's like handing the DM a wrench but forcing them to use it like a hammer. Yeah sometimes it produces good results(like random encounter tables), other times it's just simply the wrong tool for the job. At the same time, I also feel that "random" is a poor excuse for bad DMing, it allows the DM to say "well it's not my fault, it's random!" At some point, if everything is "random", why do we need the DM to roll the dice for us?