They did not “steal” it, they rolled equally as a dungeon participant and in this case not for themselves but for their friend as you noted yourself earlier.
It could be a (mini)-boost by the group if the majority decided to boot you out after you keep spamming about it, disrupting the dungeon run. There is only one part of the story here.
If additional parameters will be introduced for votekicking, it would make no difference. The VTK would still be there.
It is not considered abuse to be kicked for any or no reason.
If you do have suggestions on the improvement of the VTK you can always make suggestions about it ingame.