Took me 3 years to realize that Viola can punish Natsu's 66BBE and Nightmare's 4KK by crouching 2nd hit and then stand up and do 6A+B for massive damage. I didn't know I actually have enough time to do all that.
Since meter is required to get big damage off of 6A+B, it's probably better to just 44A BE. The 2G ~ 44 input is a bit less lenient but having 44A primed for quickdraw is half the character, anyway.
As for a string defense guide, there's
this thread, but it's incomplete. Most of the string defense guides are, partly because they're a lot of work and partly because string defense tends to be mostly independent of the defending character's idiosyncrasies.
With the benefit of hindsight, I think the smartest approach would have been to make a general, character-independent string defense guide that with information about where strings jail, what directions to step, how negative the attacker is after having the string ducked/stepped/JGed, etc., and then each player could fill in the blanks using the available frame data and whatnot. Which is really the main problem with this type of guide (I've made this error in my Aeon punishment guide, so I'm guilty as well) is the duplication of information that's readily available in the frame data. The exceptional stuff
not gleanable from the wiki is what ought to be documented; if a high string jails on block, or if a vertical string can only be stepped to one side, if a move pushes back too far to punish, that sort of thing.
If I remember to do so, I'll write up a separate post outlining in more detail how we (i.e. SA contributors) ought to approach the documentation for SCVI. If we can achieve a similar leap in the quality of information from SCV to SCVI that we saw from SCIV to SCV, we'll probably have the best documentation of any fighting game community (although Smash autists cheat by datamining their games).
