User blog comment:TheCarrotSaysYumYum/Why Lisanna is Fairy Tail's worst character~/@comment-9565035-20140417061731/@comment-7418318-20140417090456

I'll just ignore the first parts about Edo-Lisanna, since I can't make much sense of it.

By the time the S-Class exam happened, Juvia has already proven herself a trustworthy and loyal member of Fairy Tail, so I'm sure she could have found someone to partner with her, even if it had taken more effort than just waiting still someone jumped out and said "Oh hey, I was good friends with someone who looks exactly like you. Doesn't that make us the perfect team?" I guess I don't really need to mention how stupid I found that reasoning, so I? Edo-Juvia was personality-wise almost the polar opposite of Juvia Loxer, so how can Lisanna assume that she'd get along with both Juvias equally?

The blessed magic of Tenroujima is preventin anyone with the Fairy Tail mark from dying, as long as they are on the island, so Mirajane wouldn't have died for sure, Lisanna or no Lisanna. If she was beaten without Lisanna being there, she'd just have lain there unconscious until Levy dragged Gajeel to the camp, at which point the bluenette could bandage her.

Lets ignore for a moment that this fight against Kain is an anime-only addition. In this fight Lisanna was more of a hindrance than a help. Even in this so-call tripple unison raid (which goes against the rules established for unison raids in the manga... thanks lazy animeteam -_- ) she was merely the conduit to combine Levy's and Cana's powers, without seeming to add anything for herself, so even in this one move (that never should have existed in the first place, or at least been named differently) she wasn't necessary.

That Elfman would be afraid about what might happen to Lisanna, but isn't worried about Mirajane isn't an argument. If Elfman thought that Mirajane can handle Bacchus, he automatically doesn't have to worry about Lisanna either, since they were supposed to go there together. If Mirajane can keep Bacchus from doing something naughty to her, she can also keep Baccchus from doing that to Lisanna. And more importantly, if Elfman was so worried about his sisters, he'd never have taken the bet in the first time.

Yes it was Lisanna who found Mirajane, but so what? Mira burst out of those tanks on her own without Lisanna's help. Lis just happened to be there and see it. And Lamy? Seriously? Earlier Mira knocked her out with a single, pure muscle none-magical punch. The worst she can do to Mira is distracting her for a split second. And before someone argues that Mira only got sufficiently angry due to Lisanna being threatened: Despite what MS and MP have in their translations, in the original Sayla only threatened to kill the "older sister" of Elfman and Mirajane got all pissed about Sayla making Elfman destroy the guild. Neither requires Lisanna to be there.

If you really want to find arguments why Lisanna was usefull for the story-telling in the Tartaros arc I have to better examples, though both times it's just for more dramatic story-telling rather than being necessary.

First is Salya taking over Elfman. If she had just taken him with her power, it'd have been less emotionally engaging than him sacrificing his soul to save his sister. And later having Silver deliver the cloth to Lisanna makes a lot more sense than him doing the same for Natsu.