Mr. Taylor - think of it this way: Yoda only had a couple months to impart *all* 'Jedi secrets' to Luke, and he didn't even really complete that much. It was essentially a drawn out 80's training montage with more drama. So yea, his Force-fu was rather weak. The only reason he 'defeated' Vader was 'cuz the old man had a character flaw - he didn't *want* to fight Luke. Luke didn't want to believe this thing could be his father - hence the Malice with which he fought. It was a Morale thing, not a Force thing. Recall the Emperor wiping the floor with Luke, with what amounts (in the EU) as a 1st level force ability (call it an Elitist insult - one that no-one got until they realized just how powerful the Force really was).
Vader (Anakin Skywalker) had years and years of tutelage under the most powerful force users in galactic history, and he was right up there among them in power levels. So yea, if he found the right student, and found him early enough that he could be molded (you must .. *unlearn* that which you have learned!), of course he can bring down a Star Destroyer.
Luke was *nothing* until he as well, found *real* revelation.
Also, in a meta-sense - keep in mind that there was no way in hell George Lucas could have imagined the Force to all its corners in 1976, and even then, there was no way in hell he could bring the effects needed to the silver screen without looking *ridiculously* cheesy. He could not have done the prequels before the originals.
I could care less about midi-chlorians. Again, they weren't referenced in the original trilogies because they didn't need to be. The only force users left in the galaxy weren't Tech nerds who cared about the *how* of the Force, they were spiritualists. They concerned themselves with the *why* of the Force. Therefore, before the trilogy, the EU had no basis for even knowing about them - all the people who did were *dead*, their literature *destroyed*.
the prequels sucked because.. they sucked! The writing was childish, the dialogue pretty bad, and the acting .. *shudder*.. can't even call it that, really. The sequels were Pop Trash at its finest. Made to sell.