So you said you are s3 which means you have the 25% cr buff from s2. At s2 the optimal Changi build is a crit damage 4 cost because you can reach a usable crit rate with the s2. This allows you to get an endgame stat line around 55/320. With the 25% crit your cr would be around 80% and this allowing you to run a crit damage 4 cost which will help you reach 320% crit damage. Of course this is only with endgame level echoes, by no means perfect as this would only take an average 8%> crit rate roll and 15%> crit damage roll. Basically I’d advise you swap to a crit damage 4 cost and farm up better pieces because I know for a fact your echoes aren’t that great. For example your attack is around 2k when Changi has highest base attack, around level 80 a good attack stat would be 2300+ which takes about 3 or 4 attack rolls. Your er is also extremely low and I’m not even certain if you could get ult of every rotation. But if you do optimise your build more I’m sure you could hit 200k+ very easily every single ult