(Sorry for taking a long time to answer, this discussion made me hungry ^^ )
First, all of these nutriments can be found in eggs and dairy, so it supports my main point that we can get all nutriments without eating meat.
Still, some things are misleading in the article.
1- Vitamin D can be obtained from exposure to the sun, and is available in green vegetables (except D3, but the sun gives enough of it with a few minutes a day of exposure).
2- Creatine might be important for bodybuilders, but our livers produces enough of it on its own for regular individuals if we eat a balanced amount of amino acids from the sources which I mentionned earlier.
3- Carnosine. The arguments used in the article are: "This nutrient can reduce damage caused by elevated blood glucose and may have strong anti-aging effects." Thus, someone without blood-glucose problem and who does not have a lifestyle that causes premature aging is not affected by deffiency in it.
4- Omega 3. These are found in considerable quantity in a number of vegetarian food, especially in hemp seeds, flaxseeds, seaweed, beans, mangos, and other.
5- B12: That's a delicate subject. Many scientific articles arrive at different conclusions regarding its sources; there are good reason to believe that it can be found in sufficient quantities in fermented food like sauerkraut, and that the microorganism that live in our gut produces enough of it for us to survive; if we have an healthy gut flora, that is. However, even if that is not the case, supplements of B12 are found in all non-vegetarian produce substitutes like soy milk, and you should know that nowadays, most B12 that is found in animals is given to them as supplements, since the poor diet we feed them with does not permit them to produce enough. So vegan or non-vegan, the B12 comes from supplement anyways.
TL;DR
These nutriments are harder to find for vegans, but with a bit of effort one can avoid deffiancy in any of them.
Of course, eating eggs and dairy solves the problem entirely.
While this may be right you COULD, and hear me out on this one, eat meat, and not have to worry about your intake of seeds.
Soy products are still not anywhere near equal meat protein due to the estrogen-like substance in it, no matter what you say.
Besides the article wasn't about vital nutriments, just basically stating it's more efficient to just eat meat if you want to control your intake.
About the vitamin D, it's not fair to say "you get it from the sun". In the northern part of the world you will not get your daily requirement during the winter half year, which is a fact. Basically everyone in Scandinavia when being tested for vitamin D deficiency are under the line of what's recommended, and up to 10% of the population in Sweden are at values low enough to risk being directly damaging.