In One of the Touhou Labyrinth topics, I actually posted and attempted to calculate out how much damage Wriggle would do with poison, and it sure didn't appear to be too huge (At least not enough for me to consider it making up for her low damage output), but I have to give her that she's certainly not useless. She still has decent tanking ability, for one thing, so she can survive between multiple poundings with Poison. Unfortunately, her usefulness as an attacker drops
massively if the target's got any poison resistance whatsoever, as poison resistance doesn't just affect the chance for poison to be afflicted, but also the strength of the poison if it
does occur. But who knows... if she's working for you, go for it! I think there was at least a couple battles in the game where I took Wriggle along due to "Not sure what else to bring, might as well" and am pretty sure she added up a significant chunk of damage.
It is worth noting, however, that 7F's poison is
utter crap compared to Wriggle's poison (Literally it's like a fourth of the strength or something, which is horrifically low); similarly, her PAR is pretty weak too, but it is a nice little benefit if nothing else.
Anyway
it gives at least 60-75% in actuality, which is easily one of the best attack buffs in the game).
Not really. But, with that said, for the main game it sure is one of the best. There's at least four characters I can think of that I'd rather use the attack buffs of - however, it's due to the multi-target or multi-stat nature of their buffs, and three of those only show up at the very end of the game or in the Plus Disk content. The problem is that the PAR inflicted is
huge if it hits (It's the strongest PAR effect in the game, irritatingly enough). This isn't a buff you can throw around casually; you need either Meiling or another character with ailment healing, or to only use it on characters with >34 PAR resistance, because you do
not want the side effect connecting. But of course, once that's met, go ahead - her ability to debuff enemy DEF sharply is also a boon to your attackers.
Basically, she'll do better the higher PAR resistance your team is sporting, and the more focused you are on physical attackers as opposed to magical ones.