***The following is with the skill levels based in phase 3, and some of them changed for phase 4, but nonetheless:
Not really, as a PLD you only need to level MRD to lv26 to have access to the last cross-class skill from it, which is Mercy Stroke, and to be honest you will probably actually not use it at all as PLD. Realistically you only need.
As for the CNJ skills that you need as PLD, the last one you can use is Stoneskin at lv34, so yeah, you only need to take them to MRD26 and CNJ34 to have all the skills available for a PLD50. PLD doesn't use PGL skills.
There might be some skills that are in the 40s, like Mantra from PGL at level 42, but some other skills from other classes were reduced to lv36. So ok, you might need to level some classes to the 30s or even 40s, but it's not all of them, so it is far from being stupid.
Oh, also, to make it even less stupid, the amount of time required to take a class to lv35 is ridiculously low, even on a casual schedule, this is nothing like levelling in FFXI. Did you actually play during phase 3?