A lack of active mining pools would be an indication that a coin is not being seriously mined in anyway. It's fairly easy to check pool stats. That combined with a missing developer and little to no trade volume would also indicate it's not being mined seriously.
The meaning of “a missing developer” is very unclear, there are a lot of unwarranted assumptions in those three words. Apart from the difficulty introduced by the fact that the notion of “a developer” is somewhat anomalous in the context of a peer-to-peer network (there is no practical means of enforcing the notion of an “official” anything), the use of the definite article incorrectly presupposes: that an altcoin must have at least one developer to function, that a developer must be identifiable as such in order for the coin to function, that the identified individual conforms to some as-yet-undefined specification of “acceptable”, etc, etc.
The task becomes even more challenging when considering the assumptions behind the term “missing” and how difficult it will be to operationalise them as criteria when they are so vague and unreliable (“missing” from where exactly? How long is “too long”?)
I understand what your getting at, I can certainly do a better job at explaining it. In my use of the term "Missing Developer" I guess you could apply the term lack of activity. If you look at CoinMarketCap for example you will get an idea of what I'm getting at. Coins in the top 20 or 30 seem to have similar things in common, an active developer or team of developers with a well laid out action plan for the future of a coin. This usually insures an active community helping out by submitting ideas and discussing the coin among other things. It also tends to coordinate pretty closely with number of individuals mining, staking, and trading the coin as well as the coins value and price stability. A coin that can maintain or increase it's value under a healthy trade volume is a coin I think most people would consider to be alive and under development. Some people might call this a Network Effect.
While you are correct that it should be difficult to determine in the context of a peer-to-peer network in practice it doesn't work that way. People who use and trade in alt coins look to a central figure or figures and the activity of those central figures to decide if a coin is worth investing in. When you look at coins that have no central figure or group steering their development and maintenance you tend to see no activity in trading, value, or overall interest. To most people it would give the impression that a coin is dead and worthless. Whether that's the fair way to determine value is a whole other conversation. I don't believe, and maybe I'm wrong, that a mathematical set of figures, algorithms, or clearly defined numbers could determine which coins are burn worthy any better than simple review and observation of the publicly available statistics could do. Again, maybe I'm wrong and there is a better way.
I recommend you undertake a paper-and-pencil public pilot project which at least touches on as many of these issues as possible so everyone can get a sense of the likely scope and range of application of the principle. Something from the tail end of coinmarketcap's listing that fits the criteria would probably do, or something with low trading (where the term “low” is defined in numerical coin/time terms) from Poloniex’ listing (as they have a reputation for not delisting --- but by the same token, ignore anything on Bittrex as they regularly cleanse their listing, something which C-CEX has also started to do). If handled sensitively, the very task of publicly selecting a candidate alt for this exercise will probably reveal any substantial disagreements and provide a context for resolving them (assuming they can be resolved).
I can certainly make the requirements more clear but I was trying to avoid getting over technical. At the end of the day it's impossible to please all people all the time. I will work on coming up with clearer guidelines as you suggested, as I think that's a great suggestion.
