Unfortunately, the "old" way of leveling is, for the most part, currently dead, as common practice nowadays is to burn through levels quickly to at least 30 (either soloing or in Grounds of Valor groups), and then either continuing on with Grounds of Valor groups, which can be up to alliance sized, or jumping in to Abyssea early on and "leeching" your way up through the levels. Although it's an experience that I think most players should experience, the old 6-man party setup, with camps, mob pulling, etc, is currently a thing of the past given how quickly you can burn through levels nowadays.
As for Paladins in Abyssea, they were pushed to the side predominantly because of the way the hate system works. Given how powerful melee jobs are in Abyssea, it's very common for them to hit the hate cap extremely quick, to where even if the mob turns away from them, a single melee swing is going to be enough to draw the mob back to them. Because of this, the "tanks" in Abyssea aren't jobs like Paladin, but just any job that can hit that enmity cap quickly and has a high enough attack rate that they can keep the mob on them (Monk as a result became such a job). Likewise, because of the larger HP pools and the fact that very few mobs had abilities that could deal such a large amount of damage that a White Mage couldn't keep up, pretty much any of the good melee jobs out there could tank reliably if they knew what they were doing.
Designated tanks in Abyssea were pushed aside in favor of "Just let who it's hitting now tank it", and current content such as Voidwatch sort of follows that same pattern, though in some fights Paladins are still useful. Legion sort of allows for the older "Paladin tank" scenario to return, and the new Limbus areas in turn allow for a bit of the same.
My recommendation to you is to not focus solely on making "tank" gear setups and hope that gets you through, but also to put together melee setups so that you can deal damage consistently. Since Paladin has access to the majority of the same melee gear that jobs like Warrior and Dark Knight have, it's not hard to put together a solid melee setup, and in having that kind of setup available, even if you're not the one that the mob is attacking, you're still contributing a fair amount to the group.
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