http://discovery.wmflabs.org/external/#traffic_by_engine currently has absolute externally referred pageviews broken down by search engine. It'd be nice (and helpful to folks like @Tbayer) to have the option to view how the relative share of each search engine changes over time.
Oh, it looks like there has been a misunderstanding about the wording in the task description ("relative share of each search engine"). The number we have been looking at so far, e.g. in Oliver's aforementioned 2015 report and subsequent examinations, is the relative share among the overall number of (non-bot) pageviews. It seems that what has been added to the dashboard instead is the relative share among the number of all search engine-referred pageviews. (I'm not saying that the latter couldn't be of interest too - e.g. the new chart exposes a curious drop from April 29 to June 25, 2016 on mobile web, when Google suddenly fell from a fairly constant ~91-92% to ~83-84%. But the main focus of interest has been the question how much our overall traffic depends on particular search engines.)
Ah, okay! Alrighty, we're also going to add the relative scale option to https://discovery.wmflabs.org/external/#traffic_summary
@debt: okie dokie, based onit makes sense for us to add a graph that just shows non-bot pageviews and % shares (as a separate task) but we won't be able to retrospectively break down historical data we already have.