I like games where I can play the highest difficulty if I know all the rules without meta gaming (e.g. knowing which enemies are where). In my opinion a game which is not beatable on highest difficulty without luck and meta-gaming (knowing encounters beforehand) is a bad designed one. Since in DnD 5e there is a great amount of luck involved you need to have a tactic against enemies if you play your first playthrough on ironman/hard difficulty to increase your chances against bad rolls as much as possible.
There was one comment earlier stating in a typical DnD session a DM would never allow you to see enemy stats. Well yes but the typical DM is also not a machine who would simply kill you with bad rolls. At least the DMs I know always gave my party a chance to escape a bad situation if it was mostly bad luck (and not stupidity) that put us in there. I also would offer a compromise in that case. Don't show the exact stats but show it in words like "Str: Low" or "Dex: Very High" since someone with at least a bit of knowledge (e.g. nature skill or survival skill) should know that a goblin has high Dex. So we know at least what spells or skills to use against them.
And what is most important: List their skills and abilities in the bestiary with the damage they do and status effects they inflict. Again you can do this by using words like "Skill xyz: Damage deadly; target will get prone status; Dex Save". If I have multiple targets and see a skill with damage output deadly then I know exactly that's a fight I shouldn't start (yet).
If I have information about enemies I am going to encounter I can actually make tactical decisions even if it is my first playthrough and that is something I would consider very fair to the player.
