Turns out fannishness is like a gas: it expands to fill the volume you provide. Removing tumblr just meant I spend more time on AO3.
But hey, a not insignificant portion of that time on AO3 has been spent writing. Not sure how much of that productivity I can blame on being tumblr-less and how much I can blame on Winter Soldier, but they both had an impact, I think. (Ugh, do not get me started on Winter Soldier.
And AO3 manages to be less stressful (AO3 lacking in modes of communication, and kudos being the blessing to the socially anxious that they are) and more positive emotions-inducing (people like my fic! they really like it! that is always a gratifying feeling) than tumblr. So, at least until things stop being painful irl, I'm keeping away from active tumbling.