I can tell you right now from my experience of playing to level 20 as Thaumaturge in Beta Phase 3 that it is perfectly fine. They aren't overpowered, nor underpowered. They are balanced.
The potency of the THM nukes are pretty much equal in potency to that of a melees damage. The thing that sets THM apart though is their early access to AoE and traits that give them an unlimited amount of MP if used properly (Something that CON cannot do). I will admit the spell potency to MP cost ratio for Astral Fire nukes feels a tad high but once you get to level 20 and learn the trait Enhanced Aetherial Magick, the tide starts to turn more in your favor because the trait gives your THM a 10% bonus to all nukes PLUS allows for the stacking of a second Umbral Ice or Astral Fire. It is this second stacking of the Fire and Ice trait which greatly scales your damage and further allows for absurd amounts of MP regen.
In the early levels THM actually can play RDM of sorts by equipping Cure and spamming it while under the influence of Umbral Ice. You will never run out of MP and can essentially cure tank on par with a MRD or GLA. An example would be with the level 15 fight against the white demon. You can outright cure tank through his attacks while poisoned just from spamming cure and tossing in a Blizzard II every 10 seconds and you will still have full MP.
There are other strategies I could go over but the gist of my post is to say that THM/BLM is anything but underpowered. The job has its advantages and weaknesses like the others and if you think outside the box, you'll be able to do some pretty crazy things with it which other classes could only wish they could do.
The potency of the THM nukes are pretty much equal in potency to that of a melees damage. The thing that sets THM apart though is their early access to AoE and traits that give them an unlimited amount of MP if used properly (Something that CON cannot do). I will admit the spell potency to MP cost ratio for Astral Fire nukes feels a tad high but once you get to level 20 and learn the trait Enhanced Aetherial Magick, the tide starts to turn more in your favor because the trait gives your THM a 10% bonus to all nukes PLUS allows for the stacking of a second Umbral Ice or Astral Fire. It is this second stacking of the Fire and Ice trait which greatly scales your damage and further allows for absurd amounts of MP regen.
In the early levels THM actually can play RDM of sorts by equipping Cure and spamming it while under the influence of Umbral Ice. You will never run out of MP and can essentially cure tank on par with a MRD or GLA. An example would be with the level 15 fight against the white demon. You can outright cure tank through his attacks while poisoned just from spamming cure and tossing in a Blizzard II every 10 seconds and you will still have full MP.
There are other strategies I could go over but the gist of my post is to say that THM/BLM is anything but underpowered. The job has its advantages and weaknesses like the others and if you think outside the box, you'll be able to do some pretty crazy things with it which other classes could only wish they could do.