Being a "Jack of all Trades"-wannabe, for the longest time I thought I should be hiking all my skills up as equally as possible, else I don't "earn" that title.
Truth of the matter is, that's pretty much impossible. Skills like alchemy, potion, and att/def are so much easier to level than, say, ranging or tailoring.
So is there a better way to determine how well you are (comparatively) doing in a skill?
The best way I could find was comparing to other players. There were two schools of thought on this... compare to the top player for each skill, or compare to the lowest of the top 50 as that might be a better insight into the difficulty of leveling that skill. (The top player may just spend an excessive amount of time on that one skill.)
I ignored "who" had the top level (or low top 50 level) and focused solely on the numbers, as this was just an idea to compare skill leveling difficulty, not attempts to beat some other player.
This proved to be a bit problematic, due to the one thing I feel should never have been allowed: people hiding their stats. Cowards.
This was primarily problematic in the fighter skills... attack, defense, magic... as they seem to be the biggest of the cowards. Yes, I know, they do it because of PK, but I don't care. Of the top 50 attackers, for example, I believe I found maybe 3 of the 50 who hadn't hidden their stats.
At any rate, this led to my idea being troublesome to try. I eventually had to just use the lowest top 50er's skill level that could actually be viewed rather than the actual person in the #50 spot.
These are the ranks I figured out, keeping in mind they aren't necessarily the highest and lowest in the top 50 of that skill due to privacy crap.
Skill - (lowest top 50/highest top 50) level
Attack - 134/146
Defense - 139/145
Harvest - 100/127
Alchemy - 100/129
Magic - 74/101
Potion - 82/115
Summoning - 50/107
Manufacturing - 67/100
Crafting - 70/112
Engineering - 42/66
Tailoring - 31/66
Ranging - 28/36
As can be seen, there's a huge gap between the highest levels for some skills over others. They were taken a while ago and have possibly changed by now, but the point was to find a reference, not be precise.
If you're looking to be a Jack of All Trades, to see how well you're doing in a skill comparatively, try comparing to these numbers rather than attempts to keep them all equal.