Thing is, the Lovers are really hard to beat (They should give 2x treasure chests). But they are also the bosses who actually require some thought, coordination and teamwork to defeat. It's not about who is experienced in the run, it's about who can stick to a plan well enough.
It really is a 5-men job.
You need 1 to solo the Male Lover and keep him busy.
You need 1 to throw rocks at both lovers to keep them as far appart as possible and throw them on the ground, which buys anyone about 4 seconds.
You need 1 (ranged) to take out the ghosts as they come up. It's high priority, for these can really ruin your day.
You need 2 to take on the Female lover and kill her as quickly as possible.
You definitely need a crew who can stick to the job at hand and act disciplined in the face of chaos. We succeeded it at our 5th attempt with a bunch of 4 newbies and 1 guy who did it once, but had terrible lag problem who couldn't actually do anything (but he was an engineer, so he just created turrets and still helped a lot).
And the reason it needed us 5 tries was merely because in the first 3, we tried to take down the guy, and on the 4th, there was a bug that got both lovers stuck in a location close to each other so we couldn't do anything.