Tank Class for Non-End Game Content?

[Enkidoh]

Well I've levelled both GLA/PLD and MRD/WAR (with GLA my original starting class in version 1.0), and personally I think they both have their good and bad points. GLA is definitely easier to get into tanking wise as a beginner as the abilities they have early on are relatively easy enough to rotate (Shield Lob to pull, Flashx2 or 3 to get initial hate, then alternate Flash with Fast Blade-Savage Blade-Rage of Halone weapon skill combo for hate generation, and Fast Blade-Riot Blade to restore MP if needed, and use Rampart, Fight and Flight and Convalescence as the need demands), which PLD just builds on.

MRD I really hated at the start as it was more slower than GLA, and right at the start Bloodbath is pretty weak for regenerating HP. However by the time you get WAR, it greatly improves and became a really fun Job to play as. It's definitely more for an experienced player though. So really, I'd recommend to play both, but if you're just starting out, GLA all the way.

As for cross class skills, because you've already levelled CNJ/WHM, that's already made things easier for you as GLA as CNJ is the second class needed to unlock PLD and thus you've already done half the work! The other class PLD can use cross class skills from is ironically MRD, and both PLD and WAR cross class each other's starting classes' abilities, so there is added benefit to levelling both. But for GLA/PLD, at the very least I'd recommend cross classing Stoneskin from CNJ and Foresight from MRD, with the CNJ's Protect and Cure as secondary abilities (they're less useful while cross classed, but still worthwhile), occasionally alternating between the MRD's Bloodbath with the CNJ's Raise if needed. But at the very least for parties Stoneskin and Foresight.

For MRD/WAR, I'd go with Flash and Provoke from GLA which both can be very useful to improve hate generation, especially at low levels, and Convalescence, also from GLA, can be helpful when someone is healing you in a party, making their job a little easier. Then just fill the remaining slots with whatever else you like (PGL is the other class WAR cross classes from which I only have at level 8 at the moment sadly, in which case Second Wind for an emergency, and Featherfoot, which is definitely useful).

Hopefully this has helped.