Even if he immediately blocks into flame fist from whirlwind is punishable, people aren't realizing this. I made a vid here to demonstrate. I had him do the string first and immediately block to show what the AI was doing.
I'm not 100% on the frame data since it's hard to find what it is for cancelled moves like that, but as a guess it's somewhere around 10-12 frames maybe? And as for the suggested nerf of its chip damage you can further mitigate some of it just by crouch blocking as well since some of the hits will whiff. Next train of thought will probably be, well I can just cancel whirlwind into armor instead! Go for it, you can block and punish the mb flying kicks pretty easily. MB db 2 you can either backdash it (with timing) or just jump over him since it's so slow, or even just armor it since its armor doesn't last that long. Can try doing mb bf2 since it's safe, but armor can beat it.
Options like I listed above already exist in the game against other characters. One example is Kotal Kahn War God, he can't really go safely into his specials except with 114. If he does so he causes gaps, but it's on the opponent to know of said gaps and to figure out how to beat them. Which I think is a good thing.
I'm very much against knee jerk nerfs, this hasn't even existed for a week and people already want adjustments on something that is punishable but people don't seem to realize how. Also, I don't even main Liu Kang. I just like knowing how to fight characters because I love this game.