It isnt as hard as you claim it is. It isnt as easy as any other sa, but it isnt that hard either. Since round 1 is all about surviving, use ninja/talent that grants you shield before 1st wave attacks. Since last wave hits like a truck, you need to do the same. How? Scaling ninjas (kimimaro, kidomaru, ukon, tayuya, hebihime, choza, choji, anything that scales)- prolong the fight as much as you can, so you have last rounds burst when it is needed. What about chaos? It's AI, it always picks the same targets under the same cir*stances. So if your nuker wont be chaosed, then wait with casting mystery after itachi chaoses. If he is the target of chaos, use other ninjas to intercept chaos, as AI uses it as interrupt. I had to level, awaken to the max and cultivate hebihime (who was laughed at by majority during monthly event, now she saves the day) for round 1 and ukon for round 4 just for this purpose.
I'm talking here about SA HARD as a fire main, 85lvl with 45k power. With the same team, that is kabuto, ukon/tayuya and hebihime/kimimaro (both setups work) my friend at 81lvl and 32k power has beaten SA easy and normal as a wind main.
So, if you cant pass it, you are doing it wrong. Dont blame the game, this one is on your side.