I enjoyed
Arang and the Magistrate (this is really a ghost romance - it could be set in any time)
Faith (it's a time travel fusion, the thing i like about it is the relationship between the OTP)
Rebel: The Thief Who Stole The People (it IS heavy, but it's got a ripping soundtrack, and there's enough humour to even out the tragedy)
The Royal Gambler (It was serious, and there is far, FAR too much crying in the first 4 episodes, but once it settles in it's an excellent story and really well told)
Iljimae (this is just fabulous - serious and hilarious)
I also enjoyed Six Flying Dragons and Queen for 7 Days, but maybe they're too heavy for someone who isn't so much into sageuks, but then you liked Moon Lovers, and I don't think that was light at all, so maybe give them a go.