On the topic itself, a large issue is the extent to which games are randomized. IE games are a great example of this. A given encounter can easily revolve around a single saving throw or To-hit roll. If a key character gets hit by a save or die spell, you're fucked and need to reload. You can play it out for the TPK, or the near wipe leading to a TPK in the next encounter, but ultimately the game is designed around the assumption that you never get hit by such spells. Fallout is similar with critical hits. And all the combat is like this. Every dick and jane with a rifle can shoot you in the eyes for an instakill. An encounter can end in flawless victory or total defeat on the first round just because 1 roll was changed by ~10 points.
Well, in the BG series if the protagonist fails a "save vs. death" then that's gameover and you're staring at an FMV, so there's no playing it out in that case anyway.
But I think IE is based around the assumption that you
protect yourself from those spells and other dangerous attacks. Buff your saves, buff your AC, HPs, MR and resistances.
Or if you fail to protect try to mitigate the effects by dispelling the negative status. Now if the game is designed around not getting hit by them then why are their spells to bring you out of a panic or domination or pertrification and the like? Why is there a ressurrection spell? I'm not saying there aren't times when as a newbie you are insta-killed or find yourself inescapably withering away to nothing, but by and large you
can protect yourself with long-lasting spells (e.g Death Ward) which abjure negative status
before MR or saves (the other two layers) even need to kick in.
I agree that for a newbie the RNG is gonna wreak havoc but once you start to learn how the numbers work (RTFM) you realise the idea is to
work the dice rolls in your favor to lessen the odds that something bad will happen and this is accomplished by applying relevant buffs to your units and building them and equipping them appropriately.
All IE games can be ironmanned without exception and quite confidently, even IWD2 Heart of Fury. Jagged Alliance 2 1.13 can be ironmanned and so can ToEE (though ToEE is buggy so you should enforce it manually). This is because they give a
massive amount of options and either give you enough expendable party members (BG series) or grace you with a party re-creation/-composition system in-game (IWD series+ToEE+JA2) or again you're simply immortal (PS:T, with a couple exceptions). Fallout is definitely precarious to ironman due mainly to Enclaver crits, I agree.