Depends on your power?

You need to consider if getting higher refinement and charms would net more value than just more stats on 1 ninja.

As Waifuu stated, it depends on your power, and how well rounded your refinements are. Also take into consideration that what you put towards 4 starring him could also be used for possibly another meta heavy ninja. Personally, due to his revive, I wouldn't ever 4 star mine unless I managed to get lucky with an 80 frag drop of some sort. Hopefully someone who has him 4 star can give you some insight on this.

its not worth it, you will replace him eventually, right now there are plenty of better ninjas to use and buy. or if you don't want those ninjas right now, then buy power and when you get better ninjas for free you can replace him and be stronger with those new ninjas.

Well im 96k main team-using regular roshi,hidan,lm,bee or masked man team so I wondered if he is worth it but the price tag is really high for a year old ninja...and u are right metas change so better ninjas will come. Thank you.

would you mind explaining why would he become useless later on when "better" ninja arrive ?

He isn't "useless" per say. He's still very much endgame. The situation here is that it may be better (depending on the person) to invest in future ninjas rather than one you may use only situationally down the line. DPH will always be viable and good at what he does, but you also want to have a variety of ninjas, especially with high BP for war, spacetime, etc. If anyone has the resources to 4 star a ninja then I say go for it. I avoid doing it because, yes I have a ton of event ninjas, but I cant use them all, so for me 3 stars is perfect and always have a variety of comps I can run for counters, etc.

more likely masked man and also future ninja can counter hidan .

Considering the new passive of azure fang that reduces by 1 the cds of mysteries before the first action of a round basically every higher initiative azure fang in first prompt move with skewering and neurotoxin counter it now in china, the same every breeze dancer since they added blind to her everywhere lol.

That said, every ninja that can chaos or immobile him in round 1 makes him useless or counterproductive and in the future treasures there are quite a few.

He is normally on balloon event so buy some power worth of 20k ingots and you can get 100 frags for free. Not a bad deal imho.