scroll down a bit on the first page of this thread to see the values of some players that Harry put up to give you a better idea of what to rate players.
The issue is that you would know the baseline for the six players posted but unfortunately that is not enough at the moment to accurately rate someone though. For instance, Rahane in CC19 was extremely underrated to me (granted he wasn't in the best of form, but he was almost never picked by the AI and barely performed when I did). Now I could try and rate him roughly a hundred points below Kohli and check how he performs ingame again and keep fine tuning it until it works out for me. Or else, I could compare him to someone else who I feel performs at a level he should arguably be performing and rate him at that level by checking the other player's rating. All of this is of course just a teeny glimpse of what is possible with an unlocked editor in the future.
On another note, it saddens me to see the vehement opposition to the very idea of an editor on the official forums. I get that these are fans who will support the developer generally but to do so at this level is just counter productive. Sometimes you need constructive feedback and that is something I feel is lacking over there. Some of their worries like cheating online could easily be prevented by just locking the database and having just one official version of it that checks for any tampering. That would also allow for the editor to be used in normal mode as I feel easy is just too little of a challenge. Some of the other criticisms like players deliberately signing young stars or proven performers and taking them online is so bizarre as it is a lot easier to just quick sim games as one of the weaker teams and see who ranks highly in the near future or watch/ask a youtuber who does a series.
@weetabixharry Would it be possible to select the opposition squad for say, a national team? One of the main complaints from me is the AI randomly dropping their star players for no reason from series to series and even the World Cup and this could solve a big issue. Selecting the opposition team XI sounds quite good already, hopefully no more openers down at five with that feature in!