This is great! I left some comments on GitHub, but overall I'm happy to have some DCR metric utilities in this funny little repo as well as a very comprehensive notebook showing your results.
Please add a summary of the main takeaways to the ticket so our future selves don't necessarily have to click through to the notebook. Copy-pasting from the notebook is fine. It'd be handy to attach at least a pair of sources-on-the-sky plots for at-a-glance comparison to this ticket (e.g., DCR or CW with the seeing criterion for 2014-as-template vs. 2015-as-template), too.
DCR aside, it's a little disconcerting that 2015-as-template has significantly more background/noise/garbage sources than 2014-as-template despite 2015 having overall better seeing. I am moderately amused that you say in the notebook that we should consider throwing out airmass > 2 visits, yet you also wish there was a greater distribution of airmasses to improve DCR. There is a handy figure (Fig 8) in Forster et al. 2016 that shows the airmass distribution of the HiTS campaigns, which I trust you've seen, and there are a few 2014 visits with airmass > 2, but I don't think there are any 2015 ones. Both the 2014 and 2015 visits have pretty bimodal airmass distributions. I guess I would naively assume the airmass > 2 visits are the first to go when we impose a good seeing criterion, but maybe not.