Hi, if I look at a page and see that it's ranking for several hundred keywords (mostly in the top 10 that is), if I just target the same main keyword, will my page also rank for the same several hundred keywords, or is there more to it than that?
No, there's more to it. You would need to add LSI and semantic keywords within the article. It's not difficult though.
Well, it also depends upon a few other factors too, like how is your website/blog performance, speed, and optimization ratio. Also, keeping it original, unique, and readable will make it attractive to readers. Using synonyms and keywords is good & can increase the ranking chances. So, you can try it, until you try you won't know about anything, as Marketing is all about innovation, you have to test different things. Good luck.