Why are you talking about strength? I'm saying that a damage dealer with high strength will also have armor, so the advantage of a shield-user over him won't be that significant. Especially considering that his damage (and probably accuracy) will be significantly reduced, which raises the question: "who will take down the other faster?" Shields have a chance to block, which can be tied to some stat, such as dexterity. This means that the tank will also have to invest in dexterity to effectively block. Considering that he has already invested 20 points in vitality and 13 in strength, I don't think he will have many points left. And therefore, the chance to block will probably not be that great.
I mentioned strength because percentage-based armor increases effectiveness as vitality increases, as I said. In other words, 400 HP and 50% armor mean that the character will have to take 800 damage before dying. And 200 and 50% means 400 damage before dying. Although the same applies to increasing weapon strength, but, as we have seen, increasing weapon damage by two times is not the same as increasing HP by two times. That's all the math.
The problem is that this "tanky" character is designed to withstand melee attacks. He has less chance against mages and archers. Also, in the game, monsters don't always target the fattest and strongest characters. This isn't an MMORPG.