As a preface, it is a known design decision that all accessories are wearable by all battle classes. Since this is universal, it cannot be logically surmised that this design exists specifically to allow Tanks to swap around STR and VIT.
If we want to ask if the existence of Strength Tanks is good design, bad design, or a completely unintended situation that arose from the above seemingly harmless design choice, we should look at things from two angles. First, what is a Tank's "main stat" as best the game has defined for us? Second, every job has a genuine use for more than one of the six Attributes(STR, DEX, VIT, INT, MND, PIE). How does a Tank's relationship with Attributes differ from everyone else's?
Main Stat
I do not believe that there is anywhere within the game or documentation surrounding it that explicitly tells each class/job "Hey. This is your most important stat. You want this one." This is probably bad. So what do we have? Well, let's first take a non-Tank example: the Monk. It is generally accepted that a Monk's main stat is Strength. How does the game suggest this to a Pugilist/Monk?
- With no items equipped or Bonus Attributes allocated, Strength is their natural highest Attribute.
- When in a party, their Party Bonus increases Strength.
- When rolling on gear, they can only roll Need on gear which contains Strength.
Now, let's examine these aspects of the design as they relate to the three Tanks.
- With no items equipped or Bonus Attributes allocated, Vitality is their natural highest Attribute.
- When in a party, their Party Bonus increases Vitality.
- When rolling on gear, they can only roll Need on gear which contains Vitality.
When it comes to Tanks, the signs point to Vitality being the main stat. Another thing worth noting is that if you do attempt to roll Need on an accessory that does not contain your main stat, it doesn't just say no. It explicitly tells you that "This item is not suited for your class or job". Pretty harsh.
So... Joe McTank bops through to 60, seeing the signs that Vitality is a good idea, and then encounters Pug McPuggington who asks why he's wearing yucky Fending Accessories and tells him that Slaying is better. To which Joe goes wait: The accessories with Strength that the game actually flat out said were not for me are what I'm supposed to be wearing? Uh... *Heroic BSOD*
I'd personally classify the "accessory problem" as an unintended situation. The potentially bad design comes later on.
Attributes and You
We all know that Tanks like to fight over Strength and Vitality. They fight over this harder than they fight actual enemies.
...But the other Jobs use Vitality too! Why aren't they fighting like this as well?
Well, that's because Vitality isn't the main stat of any other job. To everyone else, Vitality is decidedly secondary. They'll always naturally get enough to survive what's coming and once that number is hit they don't have to worry one iota about it anymore because any additional gains in the stat will not come at a sacrifice to their main stat. Well, unless you run off and wear a Fending Accessory... but the game says those aren't suited for you. Healers get the bonus round with Piety management, but that's fuzzier because Piety is treated more like a secondary stat(or property, as the character sheet defines them) than an attribute. Still, their goal is "get enough to not run out of MP" and pursuing more does not come at a cost to Mind, their main stat.
So, what's the problem with Tanks? It's that Vitality, their main stat, is treated the same way for them as it is for everyone else: once you can survive the fight, stop worrying about it. It is the only main stat that becomes less useful at certain thresholds. This is not good. The game pushes Vitality at Tanks, yet they're the only jobs for which the stat they're pushed toward isn't unequivocally the best stat to keep increasing at all times.
Basically, we have a situation where one of these things is not like the others. This is a red flag; a probable example of bad design.
Other Observations
- It's been pushed around very recently in this thread that the "one stat to rule them all" paradigm is a approach to gear design that is casual friendly. Now, SE has done MMOs before and has obviously taken inspirations in order to make FFXIV. They, like any other seasoned MMO dev, should know that Tanks tend to comprise the lowest population of players. Isn't it unreasonable, then, for them to purposely give Tanks the least casual gearing process of any job? This is why I believe this whole thing to be an accident more than anything else.
- It is true that Tanking tends to attract people of a certain mindset. Allowing Tanks to deal more damage can attract people who have different mindsets to the jobs. Mindsets that, naturally, clash with the mindsets of the first group. They clash rather... violently. This is the most horrifying result of the fight between Strength and Vitality and the most pressing reason that SE do something about it. It's fortunate that people appear to be starting to lean toward supporting "best of both worlds" solutions that allow both mindsets to have their cake and eat it too, as it could lead SE to make a change that doesn't drive many people from the role.
- In order to properly balance the Tanks against each other and encounters, it may first be necessary to balance them against the other roles.