It  looks stylish :)

Your problem is a patternmaking one: it's more anatomically correct to raise it an inch and a half at the back and drop it at least an inch at the front as well. Depending on your shoulders, it's also possible that you needed more stitches at the sides of the neck

It definitely is a good looking tank top.  Your knit work is very neat and gorgeous.  Sorry I can’t help you figure out the problem because I’m learning about knitting myself but it’s truly a beautiful finished piece :)

Thank you for sharing this week and I hope you’re able to get some help.  Although I know they will see this I’m going to tag two of our knitters @shanibeer @neumannsalva.

The only garments I knitted are sweaters, so I got no experience with the construction of such a top. But I think adding more rows to the neck would help - in the pictures there seem to be about 20 rows. And that will change how the top sits on your body.

Have a !BEER to help you with your work :)

<div class='pull-right'>https://cdn.steemitimages.com/DQmaHThyECGhEx8tSfHZbiMFRNYjJ35K92cDgiJjkzBUaJo/One%20sip%20of%20BEER%20for%20you.gif<p><sup><a href='https://steem-engine.com/?p=market&t=BEER'>View or trade </a> <code>BEER</code>.</sup></p></div><center><br><br> <p> Hey @purlisland, here is a little bit of <code>BEER</code> from @muscara for you. Enjoy it!</p> </center><div></div>

First of all: your top looks gorgeous. The soft pink is beautiful and your stitches are perfect. I visited the pattern site and understand that you wanted a different neckline, but I have to admit, that yours is much nicer (in my eyes) and more practical in summer. I guess you will wear a sleeveless top in summer?
Sadly, I am not sure what happened with the neckline, but I also guess that you knitted not enough rows of ribbing. And when I look through the other projects I see many, who also did not achieve the turtleneck style. The one project which looks nearly as in the pattern picture shows the top on a dressform. 
https://www.ravelry.com/patterns/library/ella-3/people
And here the top sits much higher up under the armpits, so that the neckline is also higher on the neck. But its a dress form not a human... therefore I think it is also a problem of general proportions, not only the length of the turtleneck. Perhaps your top stretches too much over the bust area and/or you need a smaller neckline combined with shorter raglan lines (I mean the cable part).... But it is more likely I fantasise without a real clue. Sorry... perhaps @shanibeer can help

It looks lovely! I agree with @muscara and @neumannsalva - to get the same look as the pictures you would need to knit more rows ... but it looks perfect as it is 😍 Looking at the photographs of other projects, I see that people have created lots of variations, yours is another one. I hope you enjoy wearing it 😎