Warrior is not broken, The Coil Turn 1 fight is broken.
The developers designed it so that you are mean to feed both of the enemies the entire fight, and keep them at 1-2 stacks.
I easily tank Cadecus at 3-4 Stacks, and I die at 5. Paladins were also meant to die at 5 stacks, but at 1-2 stacks, this boss is not hard at all, just more time consuming.
To say that warrior is a Broken class, because of a preferred strategy on 1 boss fight is a joke.
Any warrior losing threat to healing in Turn 4 is also not playing correctly. The amount of extra healing required for a Warrior is almost meaningless. 1 Extra heal worth of HP after every 5 casts to keep on par is NOTHING on Threat. 1 single Overpower is enough to offset that difference.
Here is a Breakdown with more realistic numbers.
WHM Full Darklite, Thyrus.
Tanks both in 2-3/5 iLvl90 Gear.
Tanks in Equal Gear would look like this.
Warrior HP = 8500
Paladin HP = 6375
Boss hits for 3000.
Warrior takes a 3000 Hit. 8,500 - 3000 = 5500 HP Left. (64.70%)
Paladin takes a 2400 Hit. 6,375 - 2400 = 3975 HP Left. (62.35%)
White Mage heals for 2200. with Cure II. (I edited this after the original post)
Warrior gains 2530 HP. 5500 + 2530 = 8030 HP Left. (94.47%)
Paladin gains 2200 HP. 3975 + 2200 = 6175 HP Left. (96.86%)
So, if you honestly think that 2% or even 2.5% off from Max HP worth of healing required to cover the gaps is going to destroy a warrior, then you are sadly mistaken. Warrior has the higher HP needed to survive the bigger looking hits without directly mitigating them. Their form of mitigation is based on dealing more total damage (Consistently BTW!) and receiving stronger heals inherently.
If you also think that the extra healing power makes a difference in Enmity, then you are also sadly mistaken. It's not noticeable unless you are actually a bad tank, because Damage Dealers will be WAY higher on Enmity than that little bit more healing every time.
Paladins are only better because of Cool Downs, and Warriors can use Inner Beast to make up for the missing healing 3-5 fold in 1 shot.