What Charm doesn't do that defense Curl does is give Blissey an opportunity at psuedo-invincibility. After 2 Defense Curls, I don't even think a Focus Punch from a Breloom (which you should never even face as flamethrower will break a sub) can manage a OHKO. After +6 in defense which is easier to achieve than it sounds, you are nearly invincible.
You're forgetting that if your Blissey is facing a Breloom, it will spore first before Subbing or attacking, so there goes your invincibilty. When it's asleep, Breloom can Sub, then Focus Punch which does between
79.67% - 93.77% to Blissey at +2, and is a definite OHKO at +1. Sure, you say Blissey has Natural Cure, so it can switch out to cure sleep, but that removes your defense boosts, so you're back to where you started, a defensively weak Blissey who is OHKOed or 2HKOed by most physical attacks.
Also, seriously speaking, getting 6 defense curls is not a feasible idea, and your opponents physical sweepers won't be just sitting around. What about Taunt/Sub-dos or the aforementioned Breloom, who can destroy this Blissey set?
Also, contrary to what you said, a CB Superpower from Scizor does
97.22% - 112.05% damage to +1 Blissey with SR included, so there's a very high chance of an OHKO there.
@YoshiThePirate: Sorry, but Agility-zor doesn't really work. I've tried it before and it just lacks the power to do damage before getting KOed. You need Night Slash to do damage to Rotom and other resistors like Zapdos, but then you're helpless against Heatran and Magnezone. I even tried a SD-Agility Scizor (like Double Dance Groudon in Ubers) but the coverage was even more horrible.
@Tarquin: Yeah, Bounce-dos is really good, I use him myself. Lum berry is useful as you've shown, but even apart from being a good Celebi counter, it's a major threat after a DD or two with Bounce doing more damage than EQ to some other pokes.
@familyguyman: I suggest using Explosion in the last moveslot, seeing that you might as well take down something before you faint. If you do this, you might want to change the nature to Naive, to not lower Explosion's power. It also does good damage to Blissey (
68.10% - 80.12%), who can take the burn/poison, switch out and be healed thanks to Natural Cure.