[RPG] There’s a sixth world, and a fourth world. Where are the others

As a fellow GM of Earthdawn, and former GM/Player of DnD 4e I have some good news and some bad news:

1. Your player is being somewhat silly if he's actually hardcore about statistics: It's easy enough to perform a numeric analysis on Earthdawn mechanics if you really want to. There's even an article, "The Bare Bones", that RedBrick commissioned for their website; after RedBrick shut down their old site, the author republished it under the title "Step by Step". The guy uses basic excel and such to get his results, it's not hard if you have the time. Note the part in the article where it explains that the easiest way to understand why the various Result Levels of each target number have such odd progressions sometimes has to do with maintaining an X% chance of Y result level on step Z, which can be slightly complicated.

2. Your player is also correct about the difficulty of statics on the fly: performing a statistics review of your chances to do X action within Earthdawn while the game is running is pretty much impossible unless you've setup all the formulas and such on a calculator before hand. The best you can really do is to know that for every +1 the target number is over your step number you're 1 category "less likely" than before to get what you want (and the reverse for TNs under your step number). Similar to Shadowrun, the exact odds for anything other than an average roll is largely a black box of sorts. Unlike in Battletech or DnD, there isn't a single dice expression to compare all your target numbers against, so having an index card saying "X% of getting Y or more on 1d20/2d6/3d6/whatever" isn't a thing you can do. You could do it by having a separate card for each step number against all target numbers, but bleh to that man.

3. Your player is largely correct about the dying thing (from a DnD 4e perspective): It's far far far easier for a player to randomly die in Earthdawn than it is for them to randomly die in 4e. On the other hand, Earthdawn has the Last Chance Salve to try to bring people back, and it's available for a simple 60 silver each if someone in the party has Alchemy (otherwise they're 600 silver each, ouch).

Earthdawn's step system makes it so that occasionally you'll roll much higher than expected, and occasionally you'll roll much lower than expected. At the low step numbers (and low Circles) you'll roll much higher than expected more often than much lower than expected simply because there's a minimum bound on the number rolled (1, or 2 if you're at step 8 to whatever, then it's 3, and so on), and your expected outputs aren't too high. At the same time, when everyone is rolling low then mostly things just don't happen much, but when people are all rolling high then people die horribly.

To put it another way, there's infinitely more NPCs than PCs, and so when the PCs are faced off against a small percent chance of horrible death with every attack they're targeted by, eventually they're suffer a horrible death with no prior warning. The same thing might happen to an NPC opponent, but they weren't expected to survive anyways so it's not a huge deal. When a PC suffers an unexpected death with no warning at all it seems extremely unfair because the players expect their characters to mostly live from one adventure to the next.

In addition to the chance of horrible death from plain old high damage rolls, there's also the issue of armor defeating hits. As play progresses into the higher circles, characters have more and more Physical and Mystic Armor, but their Physical and Spell defense doesn't really go up at the same rate. It becomes a contest of who can armor defeat who first and get a ton of unsoaked damage. Wild West battles might be your thing, but they're not everyone's thing. DnD 4e is a game where bringing down an opponent, PC or NPC, generally requires several successful hits in a row, and the opponent can generally tell that they're going to die soon and turn on any preventative measures. So, it's a very different dynamic to get used to.

One fix for just the issue of "all these weird dice steps" and the minor but odd probability break-points they cause, is to replace the die steps with Xd3−X, where X is the Step Number. This always gives results 0–2X, with X being the most likely result in the centre of a nice bell curve. It makes the odds much more predictable on-the-fly without altering the system much at all, at the expense of having to roll unusual dice (or reading d6s differently) and an extra mathematical operation every roll (though if you're playing via Roll20 or other electronic dice roller, it's not a big deal). Some Earthdawn players cite simplicity (in terms of just doing what the book says) and just liking to get to roll all the polyhedrals as a reason to stick with the original Steps, but if your group prefers the statistical ideal enough to deal with more complicated rolling procedures, this might be a good tweak.

Most of the retconning has occurred as the present, real-world timeline has overwritten the future-history timeline of SR.

E.g. as far as I can remember, the 1999 Seretech Decision didn't actually happen. (OR DID IT?!?!?!)

Keep in mind, the timeline of SR has advanced in the Core rulebook and in many of the various sourcebooks that come out - there's usually a metaplot event or two that becomes cannon. (E.g. the Arcology Shutdown)