Garalon is a single-phase fight where you must kite the boss for the duration of the encounter however 2 tanks are still needed.
Garalon fixates on a random raid member and move towards them. Who he fixates on is determined by a debuff which can be passed between players. Therefore, you can control who the boss is following although one player cannot have the debuff all the time because it deals increasing damage to them.
Garalon's legs can be attacked and killed and doing so slows Garalon each leg slows him down more and makes kiting him easier and ensures that the kiter does not get hit by very damaging abilities that Garalon uses.
Garalon will periodically revive his legs, so killing them is something that must be done throughout the entire fight. Killing the leg also hurts Garalon by the same amount of health the leg had.
The tanks' only role in the encounter is to soak the damage from a frontal cone attack that the boss does and that needs to hit at least two players.