I don't necessarily mind that everyone winds up at similar ilevels on catch up patches - and there are wild differences between effectiveness between someone who is in full script versus BIS with raid gear but I do agree that more horizontal itemization would be great assuming there were more varied secondary stats - because as it stands now, you could make a million different pieces, but it would always lead to a hierarchy - for most classes it would wind up with whatever pieces put you right at your acc cap and then stacking crit and all the other combinations just downgrades from there.
- - - Updated - - -
To be fair, there were some rather steep climbs in WoW as well
I don't recall exact numbers but this seems right around correct give or take. The jump from Vanilla to TBC is right around the same mark you might see from 95th percentile DPS from FCOB to Creator. But it's also unfair to compare a miniboss fight like Faust in any iteration to FCOB, as the former is about a minute long burn with no deviation from start to finish. There is no downtime, and you can see parses of people with nearly 100% uptime on enhance balance and similar damage skewing buffs/debuffs. A11 and 12 would be a little more fair as both have significant downtime like some of the fcob fights such as Bahamut.