At 11th a rogue gains reliable talent and can't fail ability checks with DC 9.
yes that is the point (and why it is amazing) that is what the entire part of teh post was about
At 11th a Rogue likely has +3 (ability modifier) +4 proficiency and +4 expertise = +11. Our untrained PC has say +2 (ability modifier).
I had moved on from the rogue at this point to show what the levels of knowladge are in 5e
Our Rogue counts rolls of 9 as 10, so the lowest they can "roll" is 21. Our untrained PC can achieve 21 or 22 in about 1:10 rolls. They can never achieve 23 or greater, which our rogue does nearly half the time. (This would be true even without reliable talent.)
again move past the rogue (and see that what they have is the ability to limit the range of variable, that shows that range of variable is too high
I might not be following your analysis correctly, but from experience at the table and white room analysis an 11th rogue can achieve results with their ability checks that an untrained person has no chance at all of doing.
the 11th level rogue is where it (almost always) works... but ANY OTHER use of the skill system breaks down...
4 PCs 1 has +11 the other 3 have +1-+3 the DC is 17 (no 11th level rogues here) yes the +11 hits the mark more often (needing a 6+) but if he rolls a 5 or less the other three can still roll with varying + to try... over time where the +11 will succssed more then any 1 of those other 3 you will find it way TOO probable for the others to one up that +11 because there is a 20pt random spread...
take that +11 down to a +7 (trained +4 and +3 stat is still good) and you have that DC of 17 being 50/50... and 3 other d20 rolls for someone to get lucky on a 14,15,or even 16+...
with out that rialable talent built in the variables are too high
EDIT I should add that the core game text specifies that there's often no need to roll at all.
everytime I bring up rolling people bring this up as some big gotcha... even in threads where I explain (as I have in this one) that I actually expanded that rule and roll LESS then the DMG suggest.
WE ARE NOT TALKING ABOUT NOT ROLLING... THE POINT IS WHEN YOU ROLL...
Regarding your history fact, a DM does not call for a roll if it is something so obscure only a History buff would know it.
okay what do you use as your guidance on when the bard not trained in history, the wizard trained in history with a high int, and the rogue with the highest Int of the 3 but not trained in history should know? now ask 5 other DMs and see if you can of the 6 of you get half to agree...
this is SOOOO dumb. I get it you can make a ruling... but that is not anymore useful then 'well you can change it' or 'well you can sometimes just not roll' does not change the problem with the variable of the d20.
They also don't call for a roll if failure is inconsequential... you simply narrate researching the answer. See DMG 237.
yes still useless in talking about a d20...
its like someone said "Man, if I walk to my grandmothers house it's too far and I am worn out, I wish she was close enough to walk to" and someone said "Hey you can drive a car there" and I answer "Yeah, I can drive I just wish we were close enough to walk" then the next person said "You know you can ride a bike and it will save your energy" and when I respond "yes, I know I can uber, I can drive, I can take a skate board, and I can drive a bike... I am talking about walking though, and none of those are walking..."
if we are talking about rolling and that rolling has odd consequences because it has such a 'luck' element in the d20 then changing it to talking about not rolling is not in anyway helpful to the discussion of rolling.
you start by seeming to not understand my point of the rogue ability that i call out as awesome, then when I show all of the ways it doesn't work as well without it you want to insert said ability that i was calling out how it made it work... then you just want to talk about how when the d20 doesn't work you think just 'not useing the d20' makes the d20 work...