A warrior affects the play style of the healers so much that literally the only thing the healers can do is spam heal them. This is especially a problem with a SCH, a good SCH, will be micro managing their pet, healing when necessary, and throwing dot's on the boss (Mind you most SCH's are idiots and only heal). This is very easy to do with a PLD tank because you can rely on them to be able to take a hit or two while you cast Bio II or wait for a gcd. With a warrior tank you literally cannot stop spamming heals because the amount of damage they take takes twice as long to heal up as a pld.
People may say warriors do more damage, but in reality, with a good group the overall parties damage output will be less because you are preventing one or two people from doing damage because they are forced to spam heal.
