No kill xp doesn't matter. What matters is the moba inspired %-based system, the horrible and uninspired spell collection, the complete lack of hard counters and the completely fucked up engagement system.
We know that the game will excell in storytelling, c&c and quests. The narrative design has always been Obsidian's strongest points, but this was your one chance to make a game that actually plays well too. And you fucked it up.
I have to add, xp distribution does matter in the context of this game, because it dictates in a way how the game is played.
They could have gone down a route where XP is not the end all be all of the group possibilities. Sometimes paths with less XP can yield different rewards, items, npcs, events, etc. That make skipping combat, not only a viable option but a desirable one depending on the character you are currently playing. Instead attaching the exact same XP value no matter what you do? Lazy and nonsensical.
It could have been so much more interesting. Instead we get forced down a linear progression more artificial than the one we got in BGI or BGII.
Also the completely boring story of the world, no imagination, nothing that makes me want to play it, explore it.
Ah shit, this game makes me have unhappy thoughts. Wasted potential.
PS: As some people have pointed out, no one at the codex wants obsidian to fail (well, maybe FSM does), we are rooting for you, so will you stop fucking up already?