Some things you can try if not already done so in the mean time.
First is it consistent or random?
If consistent that makes troubleshooting easier.
Has anything system related changes between when it last worked properly and now?
What DirectX version are you running?
Try switching for one to the other in-game, even if down grading.
Set graphic to the default in-game and give things a try to get a baseline playability.
Outside of the game there are some option/ things to check
Video Drivers
Install the latest version, or maybe roll back a version to see if there is any change.
Sound Drivers.
Often forgot about but these to can cause games to crash. Same testing as for video drivers mentioned above.
Overclocking:
If your system is overlocked CPU or GPU try disabling the overclock. If this helps you can bump it up slowly until it crashes the game.
Setting Reset
Backup the Dungeons and Dragons Online folder in your Documents folder. Delete what is there and start the game. Test if problem occurs.
If not set things back up the way you like but don't change a bunch of setting at once incase the issue comes back. Change so then test. Keep going until it crashes again.
Hail Mary Option
Do a file check from the login screen.
Really Hail Mary
Uninstall the game and reinstall, letting it download the file fresh.
These seem to solve the majority of crash issue. Hope one of them works for you.
Good Luck
