So BLM on FFXIV.

[Majidah]

I forgot to add that thundaga is broken and needs to be fixed. Seriously. Thundara is fast-cast on combo and does more damage and gets resisted less often.

[Estellios]

I forgot to add that thundaga is broken and needs to be fixed. Seriously. Thundara is fast-cast on combo and does more damage and gets resisted less often.

Thundara actually is insta-cast no matter what (and Stuns when out-of-combo), its recast is lower when combo'd though. Thundaga seems to do low damage normally but if you crit the damage is ridiculous. It's best used with a well-timed/lucky Excruciate.

[Teia]

I forgot to add that thundaga is broken and needs to be fixed. Seriously. Thundara is fast-cast on combo and does more damage and gets resisted less often.

This is basically just an unfortunate result of how the two spells' combo bonuses work. Thundara's bonus is a ridiculous amount of added magic attack potency, which is why it does so much damage versus things like Ifrit. Thundaga's is contingent on it critting and even then it seems to work differently than Thundara (like a straight damage bonus or something). Personally, I think they should redo Thundaga's combo bonus into being something more reliable.

[Skies]

This is basically just an unfortunate result of how the two spells' combo bonuses work. Thundara's bonus is a ridiculous amount of added magic attack potency, which is why it does so much damage versus things like Ifrit. Thundaga's is contingent on it critting and even then it seems to work differently than Thundara (like a straight damage bonus or something). Personally, I think they should redo Thundaga's combo bonus into being something more reliable.

Now, who was it again... Kaeko? Yep, he did a lot of research on that sort of thing.
Essentially his work has shown that Thundaga in particular has +175 crit potency when comboed, and different from everything else in the entire game, it's critical damage is not capped by the 175% multiplier, it can go as high as it actually gets.