Welcome back, since you mentioned you played Order I'll list a tldr for Order Tanks only :
- Knight gives 3 Party-wide constant auras that are extremely powerful. You enable them and that is it, nothing else to do - which makes them so valuable for zero effort. They are also very tanky but they have the lowest damage. Because of the auras, you always want 1 KOTBS every party. Kotbs also have a 2H Spec but it isn't doing more damage - it is for debuffing the enemy to have less Health and increased chance to critically hit them!
- Swordmasters are the DPS Tanks if you decide to go with their 2H Spec, which is strong because they do Spirit Damage, not Physical. Their Warband spec is though to use Shields, where they provide powerful Healing - Barriers and a buff called Whispering Winds that reduces cooldown times by 5 seconds. They are also very valued since lots of classes benefit from Winds - but it can get tiring to be considered a Winds Bot. Additionally, they have other useful tools like AoE Interrupt or Damage reduction on enemies to help your healers. I would say their weaknesss is not having a good single-target knockback which is a vital tool for Tanks in RoR.
- Ironbreakers are considered the best small-scale tank due to their special mechanic Oathfriend, where you can give buffs to yourself and your selected Oathbuddy of various effects that are very potent. Oathbreakers are probably the tankiest Order Tanks - and are a great match for the current Slayer Meta as they can make the already powerful Slayers, even more powerful. Ironbreakers also have an undefendable AoE Stagger that can be very useful in Warband fights!
Keep in mind, every single Tank has access to Guard, Challenge,Knockdown or Knockback as a mechanic and tanks are considered the hardest and most important role in the game by many. They control the flow of fights in most cases and no matter which tank you choose you will be valuable to any team in the game - but like mentioned in the case of Swordmaster, missing a GOOD single target Knockback can be very frustrating in small-scale where you have to knock back enemy tanks from guarding their squishies, but they are working on fixing it.
That's a quick summary from my part - I'll let others go into more details if you are interested in more ^^
I also recommend reading this extremely good guide from Uchoo that is going to give you far more information that anyone can give you here : https://docs.google.com/document/d/1KyC ... s4yzh21q7e