if each attack gives you a second or two to react, a lot of people will fail this. If you add the requirement to pattern match in that one to two seconds, or add more conditions it increases. people can only process so much information quickly, so to do it random you need to slow the reaction and pattern matching down so players can watch and react. You want random elements so players are using judgment instead of reacting, but a lot of the reaction based gameplay makes it very hard to do so. If one person screws up their positioning, the only one who often can react is the healer if its a non-fatal attack; many times you can't, if just because they robbed you of control! (ice floor, walling people off to fight adds)
You'd have to compare him to Ozma, and he's a decent jump compared to that.There's a thread in the Dungeon forums complaining about Hashmal complaining about basically the same things people complained about with Shinryu. So are you saying Hashmal is a huge jump compared to Shinryu?
Big issue with him is obscured mechanics and a lot of one-hit attacks, even at ilvl340. His rush is just a form of calofistieri's haircut attack, but designed to oneshot anyone but the tank until ilvl 360 or something, with a much harder tell. He feels like he is a prototype to test how casual players can deal with telegraphs being removed entirely and players forced to watch the boss's attacks directly, for almost an entire fight. Its hilarious in a way because you get the sense they realized he was too tough, and more or less nerfed every single following boss to deal with it.
The whole casual SB content from a game design sense is very teaching heavy.. It's obvious every encounter is there to teach you stuff by sheer repetition rather than feeling like organic difficulty. Susano hard is there to teach you to stack, scatter, and pop gaols, Lakshimi to drop aoes and use gimmicks. Rab's bosses teach the alliance to split adds and know when to rush to your marker, with the sub lessons being stuff like recognize nontelegraphed mechanics, stick to the boss, etc. Shinryu is just an endurance test to get you to recognize a lot more mechanics than you are used to, to try and get you ready for ex level content. I don't know what people think making it harder will do.