People tend to visit blogs to read specific information related to the topic they are looking for, they may comment, and then leave, only to reappear for the next update.

Bloggers spoke to a helpful google traffic representative last year at a blogging conference due to the concerns over bouncing.

We were assured that bounce rate is meaningless when it comes down to where we are featured in page rank states, and told not to worry about it.

Website depth is recommended for keyword pick up, and url variance, so any one page website is going to struggle to compete in any way with their competition.

Google does change it’s mind frequently however, so things are always up in the air.

There is a tendency to be stuck in the mindset of “I’m a designer” therefore other tasks such as marketing are not “proper work”, as you say. Perhaps a change of job title from Designer to Business Owner would make these other tasks seem just as important.