Instead of showing the players a benchmark character, I'd show them a benchmark party. The presence or absence of certain characters - and the abilities they commonly use - can make a huge difference.
For example, our group got up to 12th level. I played the cleric, and we had a fighter rogue, wizard, sorcerer, paladin and ranger. I typically had Greater Magic Weapon spells as most of my 4th level slots, with a Deathward or two and Spell Immunity as a domain slot. I had a bead of karma. Most characters ended up swinging +5 weapon with other abilities by the end because of my spells. The paladin had a +1 Holy flaming bastard sword- so he effectively had a +8 weapon. Ouch. For the most part, our magically buffed weapons served well, since they were more powerful than we'd normally have. Also, spells like Bull's STR, Endurance, fly, and improved invisibility were passed around by our casters.
On the other hand, a group without a cleric or buffing wizard would be toast if they had our weapons.
If a character is counting on great teamwork, but it's not coming through, there will be problems. Fighter Joe might not be able to fly or see invisible, and wields a +1 shocking flaming keen holy weapon, because he counts on the wizard hitting him with fly if enemies take to the skies, counts on cleric buffing his strength and weapon, and relies on the spellcasters to reveal invisible foes. Fighter Stan might wear see invis goggles that also have darkvision, wields a straight up +5 weapon, and has magic items that provide bonuses to darn near everything. When operating with his team, Joe will be really tough, but if the group is caught offguard leaving him without buffs, or if he's cut off, he might be in trouble. Stan doesn't have the same glaring weaknesses as Joe, but will also be less effective as a member of the team.