Helena only has one safe way to enter BKO on block. However, no one is going to block everything you throw at them. So the issue is more about the risk associated with using Helena's tools rather than the tools themselves. Plus, she can't effectively link a sit-down stun into a CB or even a launcher (the requirements to do this will never happen against anyone good). Her evasion was nerfed a bit (although still decent) and she has severely limited options when she's not right in your face.
When you see some of her frame data, it will be interesting to see your reactions. I'm almost of the mindset that Team Ninja thought some of her BKO transitions would be safe, but didn't actually test them out to confirm. Either that, or they truly didn't want her to be able to enter BKO safely on block.
I also find it interesting that she still can't enter BT without using an attack or going into BKO first. She has a bunch of new tools, but they're all risky if the opponent decides to counter mid punch. I am not exaggerating when I say that Helena's bare bones strategy is to make the opponent guess between mid punch and throw. Now, if the opponent continues to guess wrong, Helena will look amazing... but the more skilled your opponent, the less likely that is to happen.
Meanwhile Hayabusa struts around with +9 tracking guard breaks, Ayane has safe, long range sit-down stuns that guarantee a launch, Eliot has parries that guarantee a launch, and Rig transitions into Flamingo with advantage on block all the time. Why go through all the effort required to compete with the other characters when it's clear Team Ninja deliberately removed Helena's tools to make her harder to play with. And by harder, I mean far lower tier, not just "get better with her".
I don't mind having to work hard to learn a character to make them mid/top tier, but no matter how much you understand Helena and DOA5 in general, she's not going to be anything other than low tier unless some sort of oddity is found like the forced tech setups in DOA4.
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