You should read an introduction to 敬語{けいご}, or honorific language. Wikipedia will do fine.
Briefly, there are two kinds of honorific language: 尊敬語{そんけいご} or "respect" language to elevate the referent, and 謙譲語{けんじょうご} or "humble" language to depreciate the referent. The problem was that you've mixed them up. The basic rule is, you never use 尊敬語 to refer to yourself or your in-group; that would sound incredibly arrogant, except people don't even do that, so that when you use 尊敬語 they automatically assume you're talking about someone else, to whom you want to show respect. And of course, you only use 謙譲語, humble/depreciating language, to talk about yourself or your in-group.
The grammar おVになる is 尊敬語, respect language. You can't use it to talk about yourself. -ておる, on the other hand, is 謙譲語 (well, in the standard dialect at least). So what you said didn't make sense. It's like saying "I humbly give you the priceless privilege of witnessing me waiting."
You can see this in the website you've linked, where the two grammar forms you've used (おVになる and おる) are in different columns. You can also see that the 謙譲語 equivalent of おVになる is おVする, so the proper form would be お待ちしています; or, as your friend suggested, 待っております which works just as fine. (You could also combine both as お待ちしております, or even be super mega humble with いたす, the 謙譲語 equivalent of する、 to make お待ちいたしております, though that's definitely overkill; your friend is correct that 1 single 謙譲語 marker is enough).
