No longer permitted in my game, after a rough experience as a DM.
Warforged build, with various other "can't kill me" powers (boundless endurance, from memory?). Yes, the player was min/max-ing a bit, but the choice of race wasn't that relevant. It probably would have been even worse if he was a dwarf.
Here's what I discovered...
1) I can't use minions, unless I metagame it. A ravening horde of greataxe-wielding orcs *cannot* hurt the 'rager. Not possible, by the rules. Unless, of course, they all stand back... drop their axes... and chuck stones (improvised missile weapons) at him. Yes, they can run past the fighter and attack all the softer targets, but there are three problems with this: not all minions should be "smart", it makes for poor narrative (orc barbarians afraid of fighting the warrior), and it's insanely frustrating for the other players.
2) Skirmishers are significantly impacted. A typical skirmisher does trivial damage to a 'rager once it's marked. Something like a panther will do 0-3 damage on a hit unless it can move away and charge every round. That provokes, which means it may not even be able to get away... and will be taking double attacks even if it does.
3) Soldiers become frustrating. The 'rager has more difficulty hitting them... but they can barely scratch the 'rager in return. Fights end up longer, which diminishes the fun.
4) The thing that convinced me to ban the 'rager for the moment was a melee solo. Big Bad Boss. Solo, three levels higher than the party. It was tough enough that it could do about a third of any PC's hp in damage in any given round (maybe more, if it critted or action pointed). But against the 'rager, it was a joke. It took 5 rounds (including action points) to take him to bloodied, and then he dropped boundless endurance (...assuming this is the power that gives regeneration while bloodied; don't have my books on me). Now it needed to hit *every* round (or score several crits) simply to keep up with 'rager. Forget any healing he might be receiving... forget any effect the other PCs are having at all... the 'rager would eventually have worn it down simply on the pure math of the thing.
Targeting the other PCs and "showing" the player how his PC is a poor defender isn't an option for me. Why punish the other players because the 'rager is nigh-unkillable? Meta-gaming lots of artillery (or minions who throw stones) is frustrating. Yes, I could hand-craft every encounter to ensure that the 'rager is being targeted by a brute, and skimishers are targeting the other PCs... but this gets artificial after a while. Fights drag on longer. And you cannot convince me that it's balanced by giving up +1 to hit.
I'll caveat by saying I love 4e, and I allow every other option available in PH, Martial Power, etc. Other DMs and players may be enjoying the 'rager in their games. But the 'rager is broken in mine, because it reduced the number of options that I could apply to keep the game challenging and fun.