I'll play Helena in casuals at Season's Beatings. If I do well, I'll lead off with her in the tournament. I can still win with Helena, I've already done this in DOA5... it's just that you have to work really hard playing the stun game and you have to hope your opponent guesses wrong a lot. You can still get 50% off of a hi counter BKO throw with environment damage.
The top players can't play Helena like they did in DOA4, and I'm not talking about the forced tech stuff. A few strats still work, but you basically can't play as reckless anymore. 1PP is your new friend, P+K is still reliable just not the end all be all crush that it used to be, and BKO isn't as worthwhile as a crush anymore. Not to mention a lot of characters can hit Helena out of BKO duck with downward striking mid attacks.
She's not the evasion machine she used to be, she's not as safe as some of the other stance characters (hello Rig), she relies almost entirely on the stun game, and she can't do much of anything from a distance. But she's still Helena, and I will mess you up with her if you're not careful.