Thoma is a brand new 4-star Pyro character in Genshin Impact, currently featured on Hu Tao's banner. He fills a niche as a shield support character, along with Zhongli, Noelle, Diona, and Xinyan, but does his shield match the strength of other characters?
Can Thoma work as a sub-DPS?
While many may want to use Thoma as a sub-DPS, unfortunately, his numbers are too low to deal substantial damage. He has an Elemental Burst that is somewhat similar to Xingqiu, dealing Pyro damage in an AoE after using a Normal Attack. However, his damage is too low to reliably use him as a sub-DPS damage dealer.
Also, his Pyro application in his Q is too slow. Genshin Impact has a mechanic called Internal Cooldown, which measures how quickly a character can apply a certain element. Thoma's ICD is slow, he only applies the Pyro element at a rate of three ticks. (i.e. when you activate its Elemental Burst effect three times.)
As a result, Thoma is sadly not a good substitute for compositions where Xiangling is used to quickly apply the Pyro element. For example, you may want to pair Thoma with Tartaglia to work similarly to Xiangling. But Xiangling beats Thoma in both damage, AoE, and the ability to activate Vaporize with Tartaglia.
Thoma shielding potential
As for the numbers, Thoma has the second strongest shield in the game. Thoma's shield will outrun characters like Diona and Noelle when your shield is constantly upgraded, as his shields recover from normal attacks with his Elemental Burst.
However, outside of a Constellation 6 Thoma, its usefulness exists primarily as a shield, which can reduce its overall usefulness. Thoma doesn't offer the utility of a shielder like Diona, who can also heal and has superior power generation for Cryo teams.
Speaking of power generation, Thoma has major energy recharge problems that you will need to solve when building it. Thoma's Elemental Burst has a cost of 80, among the highest in the game, but her Elemental Skill has a long cooldown of 15 seconds.
Unfortunately, his lack of usefulness coupled with his Energy issues makes Thoma an inflexible unit that doesn't belong to many teams. Thoma also competes with Bennett, who simply provides more utility overall. Bennett offers adequate survivability the same way Thoma does, but brings superior energy generation, attack buff, and overall greater damage.
Diona has a similar niche, working only as a shield in Cryo squads. However, she Diona excels in those roles because she can also heal and provide better energy generation with the sacrificial bow. Zhongli might just be a pure shield, but her shield is unmatched and extremely strong, also bringing some utility with her Elemental Shred to her shield and crowd control from her flurry. Thoma's kit is incredibly limited and, unfortunately, he's a weak character overall.
One thing to note is the appearance of corrosion coming in the near future. Corrosion is becoming a common mechanic, present in Spiral Abyss and as a feature of some of Inazuma's new enemies. As a result, Thoma's usefulness may be further reduced, as he brings nothing on the table other than shields.
Thoma's best teams
If you really want to use Thoma, the best way to use it is to pair it with a Hu Tao. Hu Tao doesn't actually want to use Bennett, as he gets more damage for running low on HP. So Thoma can provide a survival level for Hu Tao once he reaches that HP threshold. Additionally, your team's damage will increase, as two Pyro units in a team will give an attack bonus.
Thoma could also work with other Pyro DPS characters such as Yoimiya. However, Bennett is usually the strongest option in this case. However, Spiral Abyss requires two squads to be used, so if your Bennett is busy, Thoma could act as a substitute for your second squad.
Thoma could work to provide a level of security to Sucrose teams as well, where Sucrose is performed with a Xingqiu character and Electro sub-DPS. Generally, however, it's probably best to run two Electro characters on Thoma, but you can run Thoma if you're having trouble surviving.
