I use all of the above and many more, all have their benefits and drawbacks. All pages with groups do suck out your time and do nothing in return - if you don´t pay someone to use these groups, I´d stay away from them - into that category falls fb, deviantArt, drawcrowd and g+.
I slowly build my ground on around 25+ networks, including Patreon which is my main hub for direct output(paid and free) then comes LinkedIn, behance, ArtatArt, Artlords and Paigeeworld. More professional networks are coroflot, creativefinder, Altpick and zerply.
It takes more time than to be active in one page, but with tools such as ifttt posting can be easier. Tumblr is a special case as I post regularly but my work rather gets attention when others pick it up and reblog. I´m fine with that, if you accept that tumblr works this way, it becomes OK. Many pages like Pinterest reblog's stuff from tumblr and deviantArt - it all comes together on pinterest and similar pages like Stumbleupon then.
Right now it seems if you want your art to get seen or if your goal is a community (for feedback) you need to publish in groups on fb or elsewhere, but that is a soapbubble and you surround yourself only with artists. Even if you find groups to promote your art to potential buyers, these are either too crowded, full of spammers or nobody see´s your stuff at all. If you want commissions or sell your work, Kickstarter, Patreon, freelance platforms and business networks become more important - but then, these also rely heavily on social media networks.
Besides the whole networking stuff, posting to my blog has become the center of my attention. At the end of the day and in terms of SEO it is where all efforts on those platforms point towards.