Some of those mission enemies are better suited to straight tanking (both of the reduxes of the Mea boss in Promyvion-Vahzl, for example - hit too hard when they do hit, and AOE too much to maintain shadows well). Some of them are better suited to blink tanking (the reduxes of the Holla boss, for example). Some can be well-tanked with either (such as Ultima and his nasty Equalizer - a NIN can dodge that, and a PLD can shrug off the damage, even without Invincible but especially with it).
Regardless of mission, you need *some* tank, and you can then devise a strategy that works well with that tank. The reason PLDs have a harder time is that either a. people have to think of their own strategies for PLD tanks because they aren't posted all over forums or b. they involve more use of Hi-Potions than NIN strategies, and people are cheapskates. Both of which reasons, of course, deserve a highly sarcastic "oh noes".
However, assuming you're working with a group that a. has a strategic brain between the lot of them and b. is mature enough not to make a fuss about spending time, gil, and possibly exp on CoP missions (because *everyone* has to for these missions, no sense whining that you have to as well) ... then you'll be fine.
The hard part, of course, is finding mature and competent people to do CoP missions with, in the first place. The missions themselves are relatively easily compared to finding people capable of doing them. They're challenging, but not insurmountable. It's harder to get a good CoP static, than it is to do the missions with your good CoP static.
You don't need piles of RNGs and SMNs and NINs. You *do* need a balanced party (1 tank, 2 support, 3 damage, preferably no two of the same job, and the jobs you pick complement each other well). And you *do* need intelligence (for devising strategies, for executing strategies, and for quickly adapting to unexpected stuff) and determination.
Which is to say that your standard pickup party of people who know nothing about how to prepare and nothing about what to expect (and, being pickup, it's "take what you get" rather than picking jobs that complement each other), is going to have a very hard time, if it succeeds at all. If you're gonna organize CoP missions on these boards, post to organize a *static* to the lot of them, don't organize just one mission.
PLD can totally do CoP missions. Your average pickup group won't think so, but don't worry - your average pickup group can't do the missions anyway. Form a dedicated group that has sense enough to realize that a PLD tank can work (better than NIN in some cases, worse than NIN in other cases, but it can always work), and go from there.
And trust me, any group that would get to the Monarch Linn BC and *then* decide to kick their existing tank to get a different tank, is suffering enough in the intelligence department that they'll have quite the challenge when it comes to later missions. Don't be too sad that they kicked you.
