What you're suggesting isn't possible, so a nerf (read: rework) of her tree is necessary rather than a lazy nerf. See solutions I suggested
edit - didnt read past "what your suggesting isnt possible". Your fix of changing the skills and passives is the lazy change that doesnt fix DAI's MP issues. Which is in fact the high promotion players have a warped vision of how classes handle for us "plebs"
/edit
I may not be a coding master. But I have enough experience to say that the stat you get from promotions. A .5 to crit for example. Is easy enough to change.
To break it down as simply as I can.
Almost all games are based on some kind of database. Whether it be for stats, gear, or found codex entries etc etc.
Lets talk about stats.
There is most likely a table in the database with a defined set of stats. Created and edited by the devs.
Those stats will say something like crit chance per promotion = .5
constitution = x number of health points.
constitution = .5 melee defense
Strength = x amount of damage. (I say x cause I honestly dont know these numbers off the top of my head)
promotion with pala = cunning point
promotion with avvar = constitution point
etc etc etc
There is another table in the database that has your specific account..
It will have such things as # of promotions, characters unlocked, gear in your possession (ie heartstring bow = yes) etc
This is where it gets kind of technical
Every stat on your "table" is pulled from that first table I talked about.
For this example you have 90 rollovers with the archer cause he is your fav.
archer rollovers = 90
base cunning stat = 10
Cunning = base + archer (other rogue classes as well) = 100
So crit damage = cunning(pulled from cunning stat) 100 x .5 (stat pulled from static stat table) = 50% crit chance
Anything you look at onscreen is pulled from various tables in the database.
All Bioware has to do is change that basic stat driven table in the games database. Doing so will result in a cascade change in all subsequent tables.
The only issue will be to squash any glitches and bugs that such a change would spawn.
Then after they adjust all of the player stats so there is less deviation. They will have to balance the stats for the various difficulties with the different factions.
Realistically speaking. Since Bioware has the personnel capable of effecting such changes. They could do so within 2 months time. From the time they change the first stat to the time they release a patch with all the collective changes.
So dont say it is impossible to change numbers in a game.
For example. The changes Luke made to those annoying soldiers that blocked everything. He was not able to actually change the animation cause that is embedded into the game's engine and those associated files. But he was able to change the numbers behind the animation so that it wouldnt be as severe as it was.
TL:DR stuff - a bare minimum example of how a database works. And how easy it would be to change just one stat to change every table in a database that calls on that stat.