THFs at high lvls do not gain extreme ammounts of money at their whim. A SMART THF can, however that does not mean that its anything extravagent as well.

THF with a RNG sub can easily camp NMs with more ease than any other person out there. Widescan and Flee helps alot unless the NM spawns ontop of someone and they can get it then. Hide helps in that sense too.

They can solo AF (certain ones) and can jack coins off of Beastmen that can sell somewhat ok. 5 minute downtime with a chance of failure and death of course but its your risk. Steal Flee Hide. Using special keys and tools they can jack Coffers and Treasure Chests, but it might also spawn a Mimic to haunt you. However the keys and the tools can backfire as well like costing more than you picked out from the chest(and the 30minute spawn time after a picked chest means you harm other people that need it too).

THF in battle do not do spectacular damage per hit. You will hit 20-40ish at most alot of the time post 33 and will only do great burst damage upon Sneak Attack which has a DEX Multiplier(beware of the DEX cap where it no longer matters how much DEX you have and you need to focus on STR then). A THF is more of a skillchain closer and a hate controller than a real damage dealer.

Viper Bite and Sturmwind makes Reverbration Water Element.

Subjobs include WAR and NIN and RNG for differnet situations. WAR is preffered when monsters are not that fast running(which is rare at high lvls) because you dont wanna die on your way back, however a WAR sub means more damage. NIN sub is less damage however you get a much safer time if you mess up a SATA(sneak attack + trick attack) or pulling. RNG sub is good for certain skillchains and camping NMs. All are highly situtional. However preferance of THFs seem to be NIN => WAR => RNG and i think they prefer NIN because they die less when pulling stuff at high levels.

THFs at end game HNM super battles do nothing at all. Maybe with RNG sub they can do something but dont count on it. Most of the time in HNMing you are there for Treasure Hunter II and thats the only reason why you are there..