While most of the tanks have limited toolsets at these levels, paladin feels especially limited. The other ones get short-cooldown mitigations in addition to the -20% and -30% skills, but paladin instead gets a passive block and shelltron. You can wind up feeling a little squishier as a result, since 'burst' mitigation is generally better than the passive reduction.
Shield lob isn't really useful for doing pulls unless you're hitting singular targets or scooping up a stray that wasn't in an earlier AoE window; you're better off sprinting before entering combat (20 seconds instead of 10), facepulling a pack, and hitting it with eclipse to get aggro. If you don't trust your latency, the mobs look janky, or a healer has decided to hit you with an hot at that exact moment and ripped one of them off, following up with a second aoe is good.
While you're leveling, you usually want to be mindful of your item level versus the dungeon's. So when you hop in a new place, do a double pull and see how the damage looks alongside the healer's throughput - from there gauge whether to stick at two or go full up. Once your item level is over the dungeon's, you can usually just wall-to-wall unless you have a ludicrously incompetent healer; assume that every sprout is incompetent. You'll learn to loathe the cure sound as well, which is another sign to exercise some amount of caution with wall-to-walls in later content, though 1-50 you should generally survive with mitigation usage even if your healer is a cure i/equivalent bot. You still always want to be at minimum double-pulling, as there is genuinely no reason to have a tank for single-pulls.
Blow mitigation once you've decided on a stacking spot, and avoid overlapping rampart and sentinel. Avoid letting shelltron overcap, but otherwise you can generally feel free to use it whenever it's up on large pulls. Arm's length and reprisal can be combined to make a third "strong" mitigation cooldown, if you've rotated through the other ones; you generally want to use rampart first, since it lasts longest and has the shorter cooldown between it and sentinel. You essentially use fight or flight on cooldown, unless the pack is about to die. You generally do not want to stack reprisal / arm's length while rampart or sentinel are still up, but if you're taking a lot of damage and expect the packs to be burned down decently enough, it's fine to use then. Big pulls are a matter of stacking up your mitigation against your team's aoe damage.
Paladin has the best of the invulnerabilities, and the main use of it is to pull a ton of packs, pop it, and enjoy a bit of care-free destruction. If you get a curebot that refuses to do damage, this is obviously pointless - I usually just drop those groups, but if you opt to stick it out, just save the invuln for 'emergencies,' as otherwise the curebot can and will stand there doing literally nothing during your invuln. The 1-50 dungeons a motley crew of annoying layouts and pulls that take time to learn and evaluate each their own, but the only one that I would say is a must-know is that in Dzmael, there are crystals that reduce the damage you take by an absurd amount. The Dzmael pull is basically grabbing everything up towards the first boss, parking on a crystal, and going to town; they all take a little practice, but aren't terribly difficult in the long run. After 50, it becomes much easier (though early HW dungeons can still be a mess, as people who don't learn to spend poetics on gear will usually be underleveled).
You basically just use spirits within and circle of scorn on-cooldown, though you want to get every-other of them in a fight or flight window. Cover looks fun but is incredibly impractical, and your single-target is literally just 1-2-3, which is why I immediately drop any of the crystal tower alliance raids if I happen to get them on pld. Once you get goring blade there's more going on there, and the magic phase is what makes the class not boring; before then it's an absolute slog without much to really keep you perked up.
Shield bash is also almost totally useless. Its main purpose is as a panic form of mitigation once everything else has been blown and you need to reduce incoming damage; otherwise low blow is just the more useful stun, given that it's ogcd. Interject is important to have on your bars, as a few times you will benefit from interrupting a cast (the cast bar will be shaky, rather than solid). Shirk is not needed until you start tank swapping at max content levels.
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