From what I remember of my Japanese PT, my Lucario was still pretty useful even though I forgot to learn Swords Dance (true story, i blame my terrible jap for not realising it >.>)
From what I did though I was generally spamming the hell out of Dark Pulse and Bone Rush, both moves really help Lucario's coverage. Sure, it's not really very spectacular against gym leaders, but it's ability to destroy mooks is insane: most Krokoroks and Scraggys will have trouble surviving +1 (work up) force palm. And you get Return too.
Lucario sucking until 7th gym? Impossible. Lucario pretty much survives on it's excellent base offenses alone until it gets toys like Aura Sphere, Drain Punch and Close Combat. Unless you have some shit like Bold Lucario with 0 ivs in offense i cannot see it sucking at all.