And you think they were born at level 1 do you?
I don't but since you are talking about expeirence and levels, it is fair to point out there are no rules for level 0, so I could not assume you were adding those.
In the extremely unlikely event that happens, the rogue could have still been practicing during non-combat. And in the very extremely unlikely even that the rogue somehow levels from 1 to 2 without being able to move, it would create one of those disconnects I mentioned.
So, we must assume that the rogue is practicing hiding, disengaging from hostile forces, and running extra fast. And if the rogue is, say, planning on being an inquisitve investigator who doesn't do those things?
Ah, but they must, the class demands it. Even if they have no proficiency in stealth to indicate they know how to hide in the first place.
Very consistent.
That's what multi-classing is for
I see. I figured that would be your answer.
So, in order to learn how to move quickly and train your mind through mental exercises, you first must have a dexterity of 13. Then you must learn how to wear light armor, figure out how to pick locks, disarm traps, set traps. Learn Thieve's Cant, very important to know the secret code of thieves. Then figure out sneak attack, whatever the fluff for that is. Then learn a new skill, any skill really, even how to be intimidating. Then get really good at some of the skills you have.
Then wait a while while you actually train your ability to think quickly and move quickly, probably a long while, after all, the higher your level the longer it will take to learn some new skills... despite almost that entire paragraph happening in one level of advancement.
Seems like that might make some bad fluff. After all, all of the fighter types know how to use leather armor, theives tools can be easily picked up, Theive's Cant too with just some gold and training. Got skills already, there are a few ways to get expertise... and yet none of that will give you Rogue Level 1.
Strange, still seems like there is mechanic implied by your fluff that isn't in the game