In my personal opinion a pkiller's skill should be tested based on 3 criteria, in that order of importance:

1. The ratio of pkills/attempts - the reason being that a lot of people who post a lot of logs here seem like they are the best but in reallity they may fail 80% of their attempts which is rather sad

2. The number of solo kills - As everyone knows those are the hardest to do, especially now with all that healing

3. The characters people pkill. Just because someone kills some lvl 13 newbies solo doesnt mean anything. if you take out someone like calenril solo in mordor counts for much more :P