often times, parts of magneto's powers will be "forgotten" in order to make a story flow. in this instance, it was more like his powers were changed, giving him an increased control over the visual light in the electromagnetic spectrum while limiting his second sight. so, while it was cool that he turned dazzler's attack back on her, it became somewhat unbelievable when it turned out that her "death" was merely a visual illusion.
anyway, in this fight, it took the combined efforts of cyclops, xavier, dazzler and wolverine to take magneto out, after previous "distractions" from sunpyre, paulie provenzano, hector rendoza, northstar and jean grey. it wasn't a one-on-one fight, and wolverine, essentially, only beat a powerless magneto, who's little more than an average citizen in that pretense. still, he's come closer than most x-men ever have, even in a team situation.
also, dazzler wasn't actually switched with xavier on the cross, but she created a hard-light hologram around herself that mimicked xavier on the cross, while xavier himself was removed by jean. this was the last issue of the Eve of Destruction arc. great story, in my opinion. very reminiscent of the recruitments in giant-sized x-men #1.