So, highest AC, Hit Points, Attacks and Damage wasn't "role insulation"?
Well, I've seen some situations that might be an explanation for what he's talking about:
Round 1: Fighter runs up and starts smacking an ogre. Ogre swings back, bounces off the fighter's armor.
Round 2: Ogre walks away from the fighter and smashes a wizard into jelly.
Wizard's Player: Darnit, Fighter, aren't you supposed to keep these guys off of me?!?
A well-built fighter could be quite durable, but in many cases, that only discouraged enemies from attacking them. Having features to encourage (but not
force) an enemy to focus on the fighter, or that make it hard for enemies to get away... does, I think, help make sure that they can fulfill those expectations.
Wait a minute, Rich... If every player of 1E and 2E knows the role of the Fighter is to protect the Wizard, and it's the role of the Cleric to keep the Fighter on his feet, then how can you say "role insulation" makes it easier to play a Fighter...?
Oh, I see. In 4E, you gave made it game jargon like, "Role", whereas in 1E or 2E it's just a "job" the class does.
No, I don't think it has anything to
do with jargon - if so, he would have said, "Some folks didn't realize a fighter was supposed to be a meat-shield."
It wasn't that they made the fighter's job
obvious, it was that they made it
easier - by actually having abilities that let it fulfill that function. I think that's all he's talking about - all of the roles have more defined core abilities that ensure they can fulfill their role. Defenders mark, leaders have healing words, strikers have a damage bonus, and controllers... well, controllers are trickier, but tend to hit multiple enemies and apply nasty conditions.
Now, once can still build a 4E fighter focused more on damage than defending, in the same way they can build a 4E cleric who doesn't do much healing outside of their built-in healing words.
But the point is that those healing words are always there. The marking is always there. They will always, in some way, be able to deliver the expectations of their role, even if the player wants to focus the core of the character elsewhere.
That, I think, is all that is being talked about in terms of 'role insulation'.