I would shy away from using the opponents data. With only using our data we are atleast giving a semi-accurate depiction of how a semi-skilled person would pilot a decently tuned deck. I understand you want to add the opponents data to provide more data, thus making your sample size larger, giving the impression of more accurate data. But by doing that you're including data from untuned decks, decks of 70, 80 or more size, decks piloted by newbs, n00bs or noobs, decks with ****** land ratios, decks with bad curves and games played by people who don't know how to mulligan. So yeah, I wouldn't include that information.
I would never consider mixing opponents data with user data, but considered alone it may actually give a better representation of deck placings in terms of overall power of decks, provided there was enough data for the signal to shine through all the variance in the data. It's always interesting to compare in any case.
I would also shy away from including information from forum posters that continue to use 70 card decks with 22 lands in them.
This should be no problem, because presumably all their decks would be like that, which would just be reflected by a lower win-loss rate, but the relative performance of the decks should remain similar.
hmm, what would be really useful with these records would be the win:loss for each match-up. For each deck, the ratio for each match-up could be calculated as a percentage, then the average calculated over all match-ups to give the decks corrected ratio. This would be a nice way to account for bias due to differing ratios of good/poor match-ups, effectively removes any influence of the meta. Is that easy, or possible at all, to calculate with the record keeping spreadsheet?
I've just designed a feature that produces these tables, using some of the features already provided by MvdL. Hopefully MvdL will do a re-release that includes my added feature.
I suspect that tier list for this will be like tier lists for fighting games like Virtua Fighter where the only accurate tier lists are the ones done by the best players. Spreadsheets are probably more useful for personal records but the opinions of the better players are likely more accurate
I don't see how the opinions of the better players could be better than the combined data of the better players...