This is where many misconceive the concept of guest blogging. If time is spent chasing algorithms, manipulating search engines and following through any process in the hope to get a backlink, it is unlikely that a) you are doing it right and b) that you will really be rewarded well.
As with anything online, a content strategy should be thought through, you should understand your target audience and know how to address the readers and what content to provide within articles. If the only reason for writing a guest post to get a backlink, then the article is probably only low quality drivel and will subsequently only find a home that is equally the same.
I for one would much rather spend the time creating a fantastic, well researched piece equipped with imagery, citations and the like and be rewarded with placement at a high traffic authority blog with a link back to my site that sends targeted traffic that may convert rather than a bland, uninteresting 500 word article at a blog that no-one reads. Of course, I'm not saying that this is what you do however think of it like this:-
Why should Google devalue weight passed through a link from an article published on a blog that receives plenty of traffic, has significant social signals and a high level of engagement. Just because it's a guest post doesn't indicate that the content is any less worthy than anything else online.
Sure, if the same author bylines and anchors in links are used each and every time, then it's going to be pretty easy for Google to spot - but then, if you're doing this, then you're going about it wrong anyhow.
Write quality, unique content, identify awesome blogs to publish at, encourage audience engagement and maximise social potential. Google will never devalue your efforts if you are only thinking about your audience and customers, that's the bottom line and always will be.
You may find this useful: Link Building Due-Diligence: The Guest Blogging Checklist