This is exactly where I'm at. 100% Veteran difficulty and the dogs alone are nearly impossible to NOT contact, and they take a stupid amount of health from you as well. It doesnt help that Hadouken input works only 1/20 times.
Honest to God, I have only gotten to final form Sigma once in the last 2 HOURS, and the 1 time I got there i had half health left and I guess I was insta-crushed by the hand and the outer wall as soon as the fight started....it's way overturned and I honestly feel 99% of players will never be able to do it the way it is now. You have to basically perfect it.
Also, Sigma shouldn't be able to turn around while doing his rapid-fire hand attack.... Or shoot backwards. That's kinda crap.
Edit: Sigma 2 is much more manageable but he still takes literally like 45% health on hit. Not as much health as Sigma 1, either so it was a much faster fight.