Average: You know the archetypes, you've seen the good cards coming out. You use claydol in your decks and you know that dumping 5 pokemon on your bench against dusknoir is bad. You are familiar with archetypes but cannot make any yourself. You make top cuts around 50% of the time, but usually not nationals or going to worlds. You can build a pretty consistent list, but cannot tech your archetypes and lists with the extra difference to boost yourself to the next level.
Above Average: You are known in your state. Your name is heard a decent amount, and people ask about your record. You can build a pretty good deck, and your deck can contain individual techs and variants that allow for success (such as adding a tech pokemon line such as Mewtwo lvl X) which are chosen based on a specific metagame. An above average player can consider the metagame, tech somewhat appropriately, but is still unable to create consistently good, new archetypes or other solid decks.
Good: A good player is someone confident in understanding the metagame and also the construction of lists and others' lists. A good deckbuilder can understand the mechanics of another's engine, setup, strategy, by seeing few cards and extrapolating such information. A good deckbuilder can PREDICT and ANTICIPATE a metagame and formulate techs to respond to it. A good deck builder can sometimes make new, powerful decks, but these decks do not pan out to be steadfast archetypes.
Great: A great deck builder is someone who can finally create a new archetype of some sort. This deck builder understands the metagame and can design a new deck which is not expected or seen by many, and construct it in a way to do well in a variety of situations and in a variety of hands. A great deck builder can tailor a deck to a metagame, and a deck for a metagame. A great deck builder can quickly make deck adjustments, and formulate brand new, yet successful, lists with little time due to previous skill training.
Elite/Lafonte: This is the supreme level of deck mastery. This level of player can not only anticipate a metagame, come up with new and innovative ways to employ said tactics and deck modifications and styles, but also win with them and have others do successfully. This level of player is consistently a threat at tournaments, whose lists perform extremely well, especially when used by several or many people. An elite deckbuilder can build a deck for any metagame in any age group in any contemporary format. This level of player often introduces enough changes into a standard deck, that even an elite player's archetype deck is at least 10% different than most, if not more (often times 20-25% (12-15 cards different sometimes). This level of player has contributed to or created an original archetype, or helped introduce a standard version or essential tech to an archetype.
There we go. 5 categories that would probably be easier to differentiate skill levels and approximations. This is essentially an expanded and clarified set of RA's top 7 or so. So imagine if RA's thread had a 12 tier system instead pretty much, with the skill more evenly spread.