Weapon skill on several items or racials, maybe even a combination of both reduced or removed glancing hits from your attack table on boss encounters, resulting in an impressive increase in your overall damage output. Like a human warrior with Obsidian Edged Blade (5+11 weapon mastery) could go to zero glancing hits and even use better plate gloves
Or look at the crafted epic gear, there was literally no wet warrior dream without a Lionheart Helm in it
Itemlevel was not really a great indicator an mostly, you couldn't move up fast anyway by the fact 1-5 items (widely depends on certain bosses or raids) on a single fight dropped for 40 people.
Highest dropping world drop was Teebu's Blazing Longsword, with ilvl 65. Quel'Serrar from the Questline was ilvl 65, Thunderfury/Sulfuras 80, Atiesh 90 and several Sapphiron/Kel'Thuzad drops ranging from 90-92.
That's it, nothing higher besides the temporary weapon from the Atiesh Quest.
And if you got a legendary weapon, you ain't gonna trade if for an epic in Naxx, except maybe Sulfuras. But Atiesh & Thunderfury beat at the stuff including ilvl 92.
Tier Sets:
Dungeon 1: 57-63 (rare)
Dungeon 2: 60-66 (epic ilvl 60, rare pieces 65-66
Tier 1: 66 (epic)
Tier 2: 76 (epic)
Tier 2.5: 78-88 (epic)
Tier 3: 88 (epic)
Some funny things are the scaling of the loot from the start of a raid until it's end.
Let's take Temple of Ahn'Qiraj (40 players) as an example:
- 1st boss starts with 73, but has one shiny item with 75.
- 2nd boss drops only 76, but the weapon quest offers 79 rewards.
- 3rd boss drops 77 and again 79 quest weapons.
- 4th boss rops 78 including 78 quest items for sets.
- 5th boss has 81 as regular and 79 (weapon) or 81 (armor) quest items.
- Endboss has 84-88 as regular loot and 88 for quest set armor drops.
- The 3 optional boss encounters are a total mixed bag of candy.
If you consider that not every class always needed the highest ilvl set for every spec an the spread within a set, itemlevel would only tell you if the player is nearly fully epic and which tier of raid content he was.
But most of those talking about gearscore haven't played by that time and an't imagine how it feels like to know like mostly any player of your faction on your server.
You talk to them about progression or their raid compared to yours, see them in dungeons and even though they are from a different guild... you end up in a dungeon group with them quite often. There is no need to check someone, when you are quite familiar with him/her.