Making microfoam, when you dont know, can be very hard.
But its honestly incredibly easy. If I can teach my Father to do it, in one try, TRUST ME, anyone can do it.(And he was taught on the Gaggia, not the Vivaldi)
The tip does seem pretty short, and well, it IS. But its workable, and you can make latte art capable microfoam no problem.
First thing you need to do, is temp surf the boiler so you have full steam power, for the entire time you are steaming. If you're not temp surfing the boiler, you'll never get the results you want.
You'll need to angle the pitcher so you can use the small "nub" on the gaggia, but angling the pitcher will get the milk to spin around the pitcher, which is want you want. The first part of making microfoam, is called stretching. To stretch, you need to inject air into the milk, without making huge bubbles. To do this, you get the milk spinning, and find the spot where the steam wand is barely under the milk, the power of the steam coming out of the wand, "pushes" the milk away from it, so small amounts of air enter the milk.
Once you are done stretching, you dip the wand a bit deeper, so no more air can be injected, and you are only heating the milk, while its spinning around the pitcher.
Check out this article
Coffeegeek's Milk Frothing Guide, as it is a great guide to frothing milk. Has more info then any guide Ive ever seen, and not only shows you how to make real microfoam, but also shows you how BAD milk froth is made, AND, why you dont want to do that.