Best Abyssea parties I've had have had all lights capped, including Ruby, in fact Ruby chests are very good - more cruor and more exp per kill is never a bad thing. You're gonna get gold and azure chests too. If the party's just starting out or you've got a massive influx of new members you might hold out on the Ruby lights for TEs and have somebody going mad with Azure lights.

Though I know the frustration of getting somebody to not Ruby, but instead of whining or throwing a hissy fit (as some folks do), you compensate instead, have a good BLM or SCH to come nuke the shit out of everything, cap Azure and kill stuff quick for more chests.