I want to start by stating the philosophy behind my ideas. I feel that even though tanks are currently balanced at lv 80, there could be a few tweaks done to the leveling kits to make them feel more "complete" by lv 70. I strongly feel that the tank jobs should have their toolkits more or less "complete" by that time, not only because of the existence of ultimate content, but because moving forward, lv 70 should be the "middle ground" for the jobs, and that lv 71-80, possibly 90 in the future, can be used to further empower the existing kits through smart use of traits, with an occasional new skill for more flavour.
I wanted to compile a list of short changes to the leveling kits of the tank jobs that i think could make them more fun for new players during the leveling process, for core players who run synced content such as dailies, or veterans who run ultimate content, as well as maintain their balance at lv 80. not only that, but I believe introducing these tools earlier would help newer tanks become adjusted to using them as part of their rotation at a more natural rate, as well as building some much needed game sense at an earlier level for those who strive to do their best.
PLD: while it does not need many changes, there are a few things that can be done to make it feel smoother and adding a bit of fun.
sheltron- lv 35. this should have a base duration of 6 seconds imo, with a trait around the 60-70 range that lowers its gauge cost to 30. these changes would make PLD feel sturdier without adding button bloat.
Intervene- lv 52. introducing PLDs gap closer at an earlier level will help newer tanks with being more efficient in their movement between mobs, and can also be helpful with efficiently moving to bosses after an aoe. besides, it's a fun skill, and most tanks get their gap closers by lv 60, so PLD shouldn't be left out. at lv 74 it gets the trait to add a second charge
DRK: while its not STB DRK, the current build has potential to be fun for both new players and veterans, and it definitely needs some tweaks to achieve that.
Blood weapon- lv 30. this would help new DRK players learn about building and spending mana from the getgo, while at the same time easing the difficulty of haukke and brayflox for those who are leveling.
Edge of Darkness- lv 35. moving this back would make a few of the middle dungeons such as sunken temple and cutters cry a little more bearable, and would make room for the next skill to be moved in its place
Stalwart Soul- lv 40. this skill is extremely nice for DRK to have at a lower level. it's not too strong, and helps round out the aoe rotation of DRK, but it is unlocked way too late for a 160 potency skill. the other 3 tanks have their aoe rotations at this level, and I feel DRK would benefit from this change a lot. mana generation is already extremely limited in this class, and getting stalwart earlier would be the perfect tool to ease that problem for both older content as well as helping newer DRKs get accustomed to mana management at an earlier level. it would of course need to undergo slight changes to balance DRKs damage output at the lower levels, but it could also introduce a trait at lv 72 that brings it back to its current form, or maybe even stronger. might need to be weakened and then given a trait to power it up later, since it might be too strong for the lv 40 content.
Abyssal Drain- lv 56. if you wont make it a mana spender, give it 2 charges you cowards!
Dark Missionary- lv 58. the hole in DRKs kit (rip soul survivor) at this level could be filled with DM. there is a lot of magical raidwide damage in HW, STB and SHB, and bringing this skill to an earlier level would allow newer DRKs to get used to using it for raidwide damage much sooner, an important skill in the long run. this would also help fill DRKs lack of raidwide mitigation for savage and ultimate content as well. might need a trait later down the line to bring it up to 90 sec cooldown, as it might be too strong for the older HW content.
the hole left at lv 72 could introduce traits that enhance stalwart and CnS mana generation. perhaps making them each generate 1200 mana to help DRKs lower DPS in the lv 80 content.
the hole at lv 76 could be used for anything else the devs might want to tweak for DRKs performance, but I cannot think of anything other than a trait that makes BW 15 seconds, but i dont know how much help that would be, or if its even wanted/needed. possibly the aforementioned Dark Missionary trait.
As for WAR and GNB, I feel that I am not educated enough on their kits and playstyle to make any comments, so I would instead invite you guys to add your own ideas. I just hope that compiling a list of simple changes to leveling kits would help Square see that even with balance at lv 80, there are gameplay issues in the everyday synced experience, the new player leveling journey, and as well as for those who run savage and ultimate content synced.