Stat explanations

I'm a little surprised this hasn't been brought up yet (or at least I didn't see it).

But there is no in-game info on what crit rating of 100 means? This applies to other stats too, physical defense, skill speed etc etc.

Anyone know? Wish they had it in percentage form, so you know, crit rating of 100 on an equal lvl monster is for example 5%, etc..

Actually, there is in-game explanations for the stats. If you go to your character info panel, you can hover the cursor over each stat and see what it does.
If you mean how much the numbers will be in actual damage/defence etc. you can experiment with that. Find yourself an enemy to attack with an older weapon, then attack same lvl mob with a new weapon and compare.

Hope it helps. :)

The in-game explanations don't say how much % of your attacks will crit with Critical Rate 100, for example.

Also does the game's % chance is based on a true random distribution or Pseudo-random distribution ?

I've seen some player theorycrafting on how much each point of stat is roughly worth, but I've since lost the link. Check around the FFXIV reddits, the info would be there for sure.