Opposite really. What kills groups is over reaching, especially LBs. It's not the longer battle that strains tanks and healers, it's the blanant disregard for teamwork, and breaks formations and throw the pt out of sync.
A meteor in the middle of weights/landslide for instance will wipe your pt from the graphics spam.
Damage LB is also dependent on the combine number of members. If you have 3 dead members, save LB. It will do such crappy damage anyway, it's not worth it. Tank LB is also the only instant LB to use counter to damage, etc.
You screw everyone else if you just blow a LB however innocent. First and formemost know the content.