I fly out of DCA mostly, but sometimes RDU. I’ve found that booking from YYZ to Europe or Asia sometimes is a better deal. I will book 2 tickets - DCA-YYZ and YYZ-XXX. In my experience you have to claim the bag on arrival in Canada and recheck anyhow, so no real benefit in trying to through check the 2 tickets. These almost always send me through DTW multiple times.
Or just travel light and carryon, which is what I usually do.