I was running Knight’s for a very long time and I found that I was dying to condi more than I was to actual physical attacks. Of course it could be because of the extra toughness I wasn’t dying to physical attacks but I switched over the full berserker while taking the defense trait line with adrenal health and condi cleanse and I felt much more comfortable than full Knight’s.
In any class obviously you should be dodging or positioning to avoid damage so a big part of survivability is on the player but you should also remember that in a mob of enemies toughness or high armor ratings tend to draw aggro so Knight’s may be useless in that scenario.
I think a warrior in HoT should take the defense tree for the condi. It grants you Thick Skin and Spiked Armor for extra toughness entering and during fights. Cleansing Ire allows you to get rid of condi stacks and adrenal health grants you a huge amounts of healing, not to mention dogged march also gives you a bit of regen when you’re crippled, immobilized or chilled which is very common in HoT. Eternal Champ allows you to get stability in berserker mode so you can burst down enemies with CC skills if you decide to use that. There’s also signet of the dolyak if you want some extra toughness as well.
Honestly I think Knight’s isn’t worth it because you have some utility in the class to grant you that extra armor and if you wanted to you could grab some accessories for toughness (which I think is cheaper and easier to obtain). A full set of knight’s would give 439 toughness/armor, 2 accessories would give 220. I think a warrior should have 2500 armor at least. With full berserker’s (rings, amulet, accesories n all) and no defense tree you’d run with 2270 armor, with the defense tree 2451 armor, with knight accessories and defense 2671 armor. Full Knights armor would give you 2710 with no defense line and full berserker trinkets. If you ran dolyak signet you could add 180 toughness/armor to any build.
Note that with the defense tree, it’s on average in a fight you’d have about that much armor due to the nature of Spiked Armor and Thick Skin. There could be moments where you run lower.
Without full knight’s you also have about 15% damage increase when you crit from the ferocity as well.