Probably depends on what your 7th and 8th mons are. If you would be switching over to a xatu or slowbro, then he's probably a decent 6th, even with his lower attack you'd get to keep the extra seconds required to rejoin with subpar fighters or the time required to heal your top fighters. But if you're rolling 6+ deep on good psychics (zam or espeon) or high level dragons then probably not.
PS my only lugia is not worth powering up so this advice isn't from experience.