Miio: ok, that puts another spin on it.
It sounds like it's become a player problem. I'd talk with the players in question. The player may just be roleplaying--or he may be being a jerk, but either way you need to know which way it's going.
For that matter, it sounds like this thread is feeding into the problem. One thing that may not be clear to the warden's player is that a high defense warden isn't really anything close to untouchable. They've got high defenses, and decent damage--but nothing close to the damage the rest of the party can put out (and if not, the rest of the party is doing it wrong). Put them up against anything that would threaten the rest of the party -without- support from the rest of the group and they'll wail ineffectually against the enemy for a while and fall over.
Now, "stand back, I'll handle this" is totally reasonable from a warden--particularly if he's -also- expecting his allies to wittle down the foes with ranged attacks. But it sounds like you either have a personality issue or a communication issue (or both); -not- a system balance issue.
Now, if the issue is really -everyone- wanting to know whether the warden is more powerful than the entire rest of the party put together, I could see testing it directly (I'd want the warden player -and- the rest of the party's buy in, though). Set up a split challenge with identical forces on two sides of the room. So the party has to split--and if the warden player wants to show off, he can try to handle one side while the party handles the other. I guaruntee you, even aside from the party side of the room finishing long before the warden side does, if the challenge is at all a challenge for 3 PCs, the party will, if they hang back and let the warden solo the other half of the combat, get to see him drop and -then- get to come in to the rescue (but it might make your point--that the warden is -part- of the party, not a whole party in himself).
But if the issue is the player being a jerk and you can't get him to tone it down...it's probably time to find a new defender.
Also, Miio, it's at this point worth asking, is your husband (who iirc is the GM of group you play in) a player here? Because if so, that raises the tension by another notch.