At 120hp, Butterfree isn't too fragile, however, with an Electric weakness, this destroys ANY opportunity of doing well. With Zekrom/Eelektrik being -THE- deck played currently, there is no room for any Pokemon with an electric weakness. Being a stage 2 is also a downfall, taking so much time to set up, however, the free retreat is something to note.
With no Pokemon Power or Body, we'll look at her attacks, as they're the only deciding factor on this card. One grass energy for healing 30 from all of your Pokemon is pretty weak, when it takes a full Stage 2 to set up, and then has to use an attack to get that heal off. If this was on a basic Pokemon, or even a stage 1 with a formidable second attack, this card could possibly see niche play. Her second attack, Whirlwind, does 60 damage for GCC, a total of three energy. The effect of the attack is great, it's effectively a Pokemon Catcher.
Since she only deals 60 damage with her strongest attack a turn, Butterfree shouldn't be used as an attacker in any aspect. Even whirlwinding enemy Pokemon up to stall won't be too useful, since most current decks have Skyarrow, Switch, and multiple ways to recover energy from the discard when manually retreating (Dynamotor!). This delegates her to a support position, where Cure Powder may be the only useful attack worth using.
Building up a full stage 2, which would be roughly a 6 card tech minimum (3-1-2 / 2-2-2) just for a 30hp heal is not viable. If perhaps this was a Pokepower, or if she could heal 30 from all Pokemon, then swap herself to the bench, then perhaps she'd be a viable healer for google/Truth variants that utilize Reuniclus.
With Reuniclus damage swapping, a well placed Cure Power could potentially heal 180 health, 30 from each Pokemon, per turn. Again, the downside is that no damage is done that turn to the opposing Pokemon, nothing to stall since Butterfree is likely to be KO'd that turn, and it forces a retreat of the previous tank that would be running just to get Butterfree in the active spot. This huge downside, along with being another stage 2 inside a deck that runs two full stage 2s already just spells the end for our little Butterfly. The only other option that could be possible is in a Mew Prime deck so that it can be lost zoned for Whirlwind abuse - but there are stronger cards for that, I'm sure, such as Luring Light that takes two less energy.
I'd give Butterfree a 3/10 as a full card. She doesn't fit in anywhere currently, and Cure Powder isn't too useful at all.
Art-wise, I give her an 11/10 because I love this art for some reason. Her abnormally large head gives it a cute look, sort of like a bobble head. Megaphone and I keep this Butterfree in a soft sleeve pushed into a hard top-loader in our binder as a 'show off' card. Her nickname is just "Big Head".