This is so true. I have played with tons of PLD tanks and MNK tanks of varying strengths. In my opinion, PLD is still the better tank overall.At this point I think people are giving MNK's wayyyy too much credit.
While MNKs can tank and deal good DMG, they take way too much DMG and become a massive MP sponge. Giving /NIN to MNKs still doesn't let you avoid all attacks. High HP and -PDT sets are nice, but MNKs still aren't self sufficient enough for that to matter. Fighting mobs with high attack speed, ACC, DMG, and/or multi-hit, MNKs become a burden on the mages. Some people may argue that MNKs have the Chakra ability, but even with a great VIT build, and Chakra Recast and Invigorate merits, Chakra still is only usable every 4min 10sec and only heals a few hundred HP and up to 400 regen. All that can be taken away in the matter of seconds and as I said, once every 4min 10sec at best. Also people may argue that in abyssea, mages have massive MP pools and tons of refresh. This may be true, but its not even close to infinate, especially when they have to spam heal Cure V/VI.
As for PLD, they can take hits much better then MNKs and keep themselves alive for a long time without spam cures. As such, mages can save their MP for buffs/debuffs/nukes/etc. Sure PLD isn't even in the same league as MNK in terms of DMG output, PLDs can still deal a moderate amount of DMG. Add that to the saved MP and time, otherwise wasted on spam cures for a MNK tank, now able to be used on nukes, it can easily make the fight go just as quick, if not quicker, while going much more smoothly with less risk of failure.
If given the choice, I choose a PLD tank over MNK tank anyday even if the PLD's gear is average and the MNK's is well above average. The only thing that may be an issue is enmity, which even MNK tanks have that problem sometimes. If the PLD actually puts some effort into tanking, he/she can overcome the issue.
It would be nice though if SE adds some new enmity stuff for PLD. One thing that would be nice is if they made the enmity caps for PLD higher then the other jobs. Also, SE should give PLD an ability equivalent to Provoke.
All-in-all, in my opinion, if you have a PLD tank any mob in the game, then did it a second time on the same mob, with the same allies, same day of the week, same weather, etc., but with a MNK instead of PLD, the fight with the PLD tank will be better atleast 95% of the time. Anyway, I do believe completely that PLD is a better tank then MNK, I still think MNK is the second best tank. "What about NIN?" you might ask. Well I absolutely HATE NIN tanks and I would sooner take a DRK/WAR with souleater, last resort, and berserk up 100% of the time to tank a lvl99 HNM with a lvl10 Galka PLD with a 0 healing skill, and -50MND as the only healer, then willingly take a lvl99 NIN with me to fight something even as easy as a Tiny Mandragora.
...Sorry about that, but as you can see, I really hate NIN...
Back on topic, people are saying recently that PLD isn't even worth having anymore, but I strongly disagree. Even though PLD isn't as great as it used to be, in comparison to other jobs, it is still the best tank out there.