I'm talking about the fact that you should, for example, get a fixed amount of exp for getting rid of them regardless of how you do it.
That sounds dangerously close to the PoEs do things, which would be bound to upset some. Of course, they could always count how much XP killing gives and give just that for making them go.
However, even if there is discrepency in XP gain, I don't think it is a bad thing as long as the discrepency isn't too bad - as long as player who chooses diplomatic options won't lag behind enough to struggle with later content, or if player who often confronts enemies finds himself lvling up too fast.
And what if discrepency is intended? What if we get to encounter the ruffians later in the game? Perhaps we forfit for XP and items now, but get more minor content later?
Not to mention that you can get rid of them with "diplomacy", force turn-based mode as they are leaving and STILL kill them and get the kill exp reward, too.
Unfortunately, with XP being given for different outcomes, with enough systemic freedom there will always be a way to stack multiple outcomes together. The only solution I know is like you mentioned is limiting XP source - like Deus Ex1 or PoE1&2, which IMO is a more elegant design. Alas, some people get offended if there is no XP for killing stuff.
Broading Tyco's point, XP management is generally lacking. I don't like how fast you can outscale the content in EA and I m frankling concerned about how larian would handle the difficulty.
I wouldn't worry about it too much. Raise your concern for feedback purposes but don't loose sleep over it. As long as Larian keeps a track of XP available in each chapter they can adjust numbers for 1.0. Right now we play early access build. Stretching 4 levels over entiretly of the content would be greatly undesirable. As they add content, encounters and stuff the progression will get thrown off anyway. The chapter isn't even completed so it's not like they have solid content they can balance.
Having overabundance of XP is an issue in many RPG, but Larian has been pretty good with encouraging more thorough play - I hope they will continue this trend. Favouring a "crit path" hasn't been their philosophy so far.