Fastest way to level as a Tank is use XP boosts (Aetheryte Earring, Food, FC bonus and Squadron scroll) and spam the highest level dungeon available to you.

Since you'll have fast queues it will beat out HoH due to the bonuses you'll be getting from kills. Should be even better in ShB since they're upping the exp that mobs will give in dungeons (While also removing Chain Bonus, so your EXP boost items will have a larger effect. As well as improving your EXP gains when you're not the minimum level for the dungeon as that's the only time you get Chain Bonuses)

Of course, do your Daily Leveling Roulette too (50/60 Roulette can also work, it just doesn't always give a notable amount more than spamming specifics with xp boosts). Maybe also Daily MSQ Roulette (Though, I'm not sure if it's actually worth the time it takes to actually go through)

HoH spam is only good for DPS jobs, since their DF queues will be too long to get good returns (Though, if you can run with a static, or at least a Tank/Healer friend you can mitigate that)