I know what you mean and i feel your frustration. To counter this issue, i made a macro i used when i start a dungeon. This is my macro :

"Hello, nice to meet you.
DPS, please FOLLOW THE MARKS IN ORDER.
This IS NOT WOW.. It's FF14.. don't be n00bs and FOLLOW the numbers"

Ok honestly, these lines were not like that, but after i read your post, i will make some changes and this is what my macro will say !

Now, if after that, stupid DPS still don't follow the numbers... I will talk to the other players and make a deal with healer. I will not tank and healer will not heal the stupid DPS. After he dies 3-5 times, he will either follow the marks or leave the dungeon.

Don't be afraid to step up and LEAD.

Party will appreciate this. trust me.. i had to do it about 5-6 times.. and some left, but those who stayed, they appreciated.

As a tank, you need to lead your party and sometimes, you need to educate some people...