I see comparisons like that alot but it's a very deceptive comparison.
Single encounter: level 5 Half Orc Bear Totem Barbarian (18 str, 16 con, 14 dex using a greatsword) eHp vs a +6 attack enemy = 220 eHp. He will be making 2 attacks @2d6+6 damage at will.
Single encounter: level 5 Hobgoblin Abjuration Wizard (18 in, 16 con, 14 dex) eHp vs a +6 attack enemy = 85 eHP before shield and in combat abjuration spells get factored in. He will get a few level 3 spell uses before mostly doing 2d10 with his firebolt cantrip.
When it comes to tanking it's not just about how much damage you can soak over the whole adventuring day. It's also important how much you can soak in a single combat at your best. It's about how effective healing is for you (Healing is very effective on a raging Barbarian but not nearly as good on an abjuration Wizard). It's about how much more eHP your hit dice can grant you (this is never factored into these comparisons and it's very much in the Barbarians favor) It's about how much of a threat you are (and not just when you have full resources). It's about whether you are willing to put yourself in positions where enemies can hit you and want to do so.
So I'll have to disagree. The tankiness of abjuration Wizards when compared to Barbarians and Fighters and even clerics tends to be highly overrated because they rate lowly on so many important tanking parameters (at least before much higher level).
Or maybe a better way to put this in perspective. In a single battle the Barbarian will only have lost about 6 hp from attacks before the abjurer wizard will lose his special abjuration shield (provided no abjuration spells are being cast). By the time the Barbarian loses 12 hp total, the abjuration wizard will have lost 14 actual hp (provided he's not using resources for extra mitigation).