There has never been an option to report for being kicked from a dungeon. That is not a “customer service” issue. That is a Game Developer issue with the game systems they have designed and the policies they have in place. CS does not make the rules or the report options. There is nothing against the rules for kicking you.
As annoying as it is, it is not against the rules to kick a person for no reason, or any reason. It is not against the rules to multibox either, as long as it is all manual.
What you want is a policy change by the game team which is not going to happen by posting here.
This forum is an Information Desk to help folks navigate the support system, explain policies, and explain account services. It is a SUPPORT function, not a SERVICE function.
Yes, your only option in that situation, under current policy, is to leave the dungeon and take the deserter debuff. You can also put their chars on Ignore which should help prevent future group finder matching with them.
If you would like to propose a change to the current policies, you can use the in-game suggestion feature to suggest the Game Devs change the kick system, or add an option for additional reports for non-participation. Your other option is to use the Discussion Forums - probably dungeons and raids, to make that suggestion. They won’t answer you directly but that is where feedback is collected.
CS and certainly this Info Desk, has no say in game policy, game options for reporting, etc. They also have no role in passing on suggestions or feedback to the game teams.