Design theory from someone who actually practices it... intriguing concept.
There's a new blog post up over at the Cryptic Studios Blog by Geoff Tuffli, one of the Combat Systems designers, which discusses a few conventions of game design and makes for a pretty interesting read.
Convention 2: The players character gets better based on the time played.
Regardless of player skill and barring non-formative gameplay, the more time a players character is played, the better in absolute mathematical terms that players character will get. Computer-controlled opponents that were fearsome yesterday are a pushover today.