My dex determines the % to hit and that number is locked in place it does not change for any reason until you change your dexterity.
The game adjusting 49% to the enemies status, isn't changing the 49% in the slightest, it's only changing how the 49% gets applied.
In my case a 49% chance to hit an enemy gets fired out every shot, the game then takes the 49% and adjusts it accordingly, but the shot is still a fixed number of 49%.
It's like engraving an arrow with the letter A on it. When it's fired from the bow, nothing will change that A unless you manually change it.
So in comparison, the letter A is set in the arrow but yet people are saying that the letter A gets changed to a D when being fired, just because an enemy is level 50 or has some sick armor or status or no armor or status.
The arrow is going to remain with an A on it no matter what.