This is a translated quote from an interview with Yoshida so Im not 100% sure on the accuracy.

Yoshida: We'll be making effort to eliminate that as much as possible. Within the content, there are strong and weak points to each job. For example, in the second area of savage, a paladin main tank should have higher stability than a dark knight. Depending on the player and their skill level, each party will see different results, but we'd like to reduce the difference. We can't just make adjustments to jobs based on whether they are strong or weak in particular content as that would break the jobs, so we'll work to eliminate disadvantages to certain jobs as much as possible in the content. That doesn't mean we won't be making any adjustments to jobs in the future, but we'd like to also hear feedback after playing through the different content in patch 3.1.

Source: http://www.bluegartr.com/threads/126902-Famitsu-Interview-Translation-Yoshida-on-Patch-3.1-and-Beyond?p=6560729#post6560729

In short, the problem is the content doesn't cater well to PLD's strengths and as such simply buffing PLD would likely make them overpowered in future content where PLD's strengths become more prominent in mechanics. Its an encounter design issue rather than a Job balance issue.