LUS used to schedule DCA as an OD airport. However, following the slot swap with DL, DCA became a true hub airport, with what is now about 240 (last time I checked) daily flights, and it's scheduled as such. As others have noted, with only something like 16 actual gates (the hell of gate 35X actually doubles the daily flight capacity), it's pretty amazing that AA is able to move so many people and operate so many daily flights from the airport, which only has 1 usable runway for aircraft of all sizes, and an additional one runway for express aircraft (or the occasional E190 or 319, depending on weather).

The only issue I would ever have with a DCA connection would be a delayed inbound flight. All gates can be reached within 10 minutes, even if you have to take the B/C shuttle bus connection. However, if your inbound and connecting flight arrive/depart from the same concourse, you can reach your connecting gate within two minutes. There are some flights that reliably depart from the same gates. 50 seaters all use gate 35X now, and shuttle flights all depart from the B concourse. You can use your favorite flight tracking app or even AA's flight status to see where your particular flights arrive/depart from over the course of a few days to get a good idea of what your connection will likely look like.

DCA is a great airport.