How is ilvl an issue while leveling?

[Nestama]

Being i270 in castrum abania is fine as long as you know what you are doing

I disagree, especially if it's a tank and/or healer. A tank in full shire gear means the healer has to work extra hard just to keep them alive (especially against the final boss' tank buster that gets enhanced two times) and it also means DPS will probably need to intentionally play poorly (Level 68-69 weapon > Level 60 weapon) just so they don't rip hate and force the healer to work even harder.

When it's a healer, they heal for less, which means they'll most likely spam their {Heal} II spell and then be OOM pretty quickly.

When it's a DPS, the dungeon just takes longer. So unless the boss has a DPS check (or the tank mass pulls), no issues will arise... but don't be that DPS.

Trash mobs from Bardem's Mettle and on hit pretty damn hard. So always try to be in up to date gear, otherwise you're just going to be an inconvenience in some shape or form depending on your role.