I would hardly recomend you that dont do this, stoping the progress of random party memmbers on purpose is a great offense and it could have serious consequences.

You asked if people do this? well they do it, but the should never do it.
It happened to me. I was with on a party with random party members. We were on room 49 when one guy said to another one ( possible premade ) that he wasnt going to have the full upgrade on time and asked if we could wipe, the orther guy agreed and so he pulled everything he could and trigger the traps, we had no healers, both died really fast and me and the blm did our best to stay alive but we fail.

I reported this 2 guys, and I got an answer from a GW inmediatly, he told me that I did the right on reporting this. Stopping the progress of ramdom ppl on purpose is reportable.
While just leaving the duty and "screwing over" your party may be a dick move depending on the circumstance, there is no way it will have "serious consequences" purely because of the "may be" factor. Sometimes, people just have to suddenly leave a duty. They aren't just going to ban or otherwise punish players for that (other than with the DF lockout).