Well, your link is that guys opinion, could use as a guideline, but there are some obvious mistakes in it. In general, he gets it mostly correct. It also depends on how the party is set up, with buffs and debuffs moving classes around on that list.
Most raids are set up for Physical DPS, so Magical DPS generally suffers.
For straight out healing the Druid/Warden is still tops. Though Druid/Scout has some good stuff to offer.
You didn't say why you liked casters, but you might consider a Scout if it is because you like ranged attacks, or, and this is going to seem odd, a Champion, slower than your typical caster, but tougher, and it's skills are very similar to those you would expect from a "caster".
The actual subject is much more complex, I normally advise people to try various classes before spending any money on one.