The only problem I have with vegetable stocks , is that unless you follow a specific recipe, it comes out different each time, which isnt a bad thing. But, if you want consistency on any recipe you are adding it too, remember which recipe of vegetable stock you are using, and write it down on the recipe you are adding it to.
I've found , just as Addie mentioned, that adding a vegetable bullion ( or something of that sort) to the stock definitely pulls it together. Without it, to me it tastes kinda empty. Only exception Ive found, is if you add mushrooms. They seem to be able to add enough flavor to fill in all gaps.
Just as a side not, IM vegetarian 25 years, and also an avid gardener, so Ive been doing it forever, and have added just about everything in the garden ( at one point or another) to my stock.
I was watching Jacques Pepin once, and what he does is everytime he has spare vegetable scraps, peels .... he tosses it in a container in the freezer. And then when he needs to make a vegetable stock, he just tosses them all in the pot, with some herbs, salt ...