The problem with Helena, based on what Bryan tried, is that she's doesn't have as many opportunities for guaranteed (i.e. uncounterable) damage compared to the rest of the cast.
As for Rig, don't be surprised if he does end up being really good. Based on what people who've tested the game are saying, the new characters are second only to the VF characters in terms of viability.
Personally, wouldn't be surprised if the initial tier list comes out as:
-VF characters
-new characters
-grapplers
-ninjas
-everyone else