TL;DR Above average Vietnamese for the area
Food - 4/5 - I've been here a few times and have had their pho, vermicelli noodles, broken rice and some delicious monstrosity of fried noodles I can't remember the name of (that was a couple years ago). Every time I go, the flavors are on point and I walk away full and happy. The broth of the Pho is certainly well above average for the area and the quantity of meat is also well above average for the price. Get the small if you aren't super hungry, the normal/large should fill you up if you are. Vermicelli with the fried rolls was delicious. The only thing that was just okay was the broken rice. It just did not stand out to me, the flavor was a bit lacking. After traveling Vietnam for a few weeks, I think the US does Vietnamese food relatively well (though with less variety) and Doan's is no exception.
Service - 3/5 - Nothing stood out, but no complaints.
Ambience/decor - 3/5 - It's in a strip mall, and that's what it felt like. I generally don't go to places like this for the feel of the place, just the food.
Price - 3/5 - A bit expensive for the type of food, but I think that's common in Charlotte. Places in Charlotte that serve cheap-to-make food don't usually push enough volume to make a profit unless they charge higher prices.