I can't say I've ever experienced it on my 6800 levers but I've never adjusted mine "in" as they're still sitting waaaaaaaaaay out in front of the bars as I got it from the bike shop. I think I've meant to adjust them "in" a bit about a million times but I just never have. As they're so far away, I've never even come remotely close to rubbing the back. That said....I always find myself reaching for the levers when in the drops and I have pretty big hands & long fingers so that's saying something. (Maybe I'll adjust them in soon....next year)

Anybody else ever wish Shimano had bigger shifter paddles like SRAM? (I do. Or maybe somewhere between SRAM's flag & Shimano's "barely there" finger tab)

(shrug)