i know about the happiness evolutionOk, well, having just finished the game with my own Lucario, I have some issues with your thought process.
Granted, I went a MUCH different route than most with Luke, but I found him rather useful from start to finish. In fact, he was my MVP.
My Experiences with Luke:
1). Had a Lv10 Lucario before Cheren. The Quick attack spam was easy to handle as I disliked Counter. Yes, I ran for what felt like hours before Riolu was happy with me, but he was better than most of my other options.
2). I grinded in the Battlle Subway multi train to get 12BP. It was very easy as my partner had mons that outclasses most of the foe's mons. In about an hour, I had enough BP to but Brick Break.
3). I've found Special Luke to be not very good, in my honest opinion.
Disclaimer: I am not here to insult or fight because I can see that your expieriences and mine are opposites, but I just wanted to post my thoughts compared to yours in order to achieve a differnet perspective.
i think i did remember saying sometime back a few months ago that Lucario had game-breaking potential because technically speaking you can get it as soon as L6, which utterly steamrolls earlygame because of ridiculously high offense, speed, bulk, etc.
brick break is useful as a stab but you can't use subway as an argument unfortunately. it's pretty annoying considering there are some pokemon who could make pretty decent use of BB early on (things like Electabuzz, Pignite and Darumaka), it just so happens that luke is one of the biggest benefactors of it. :/
@Brood: while in the past i'd probably agree with high volca, these days i'm leaning towards mid instead. signal beam is stupidly strong but it can't kill everything, that's not including just how many god damn types resist bug (six types urgh). this impression is somewhat skewed from using darm since darm's flare blitz is essentially disguised as the 'instantly win your opponent' button.
@cant say: how did you miss cobalion it's right on the way to lacunosa, all you need is to just detour back into his clearing o.O aside from that, cobalion is pretty good imo, he sees immediate use against drayden as a good physical tank and you can immediately dump work up (and maybe volt switch for lulz) onto him.