Check out the patch notes for the v20 Lovely Update here: http://maplestory2.nexon.net/en/news/article/55909/lovely-update-v20
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When empowered by Cunning, Blade Dance gives you a brief 1-second period of increased evasion chance. This goes from about 60% at level 1 to 99% at max level.
Meso Guard is 4s at all levels. It's 12s when empowered by Cunning, and also gives an 11% damage boost (+4% per level) in addition to its damage reduction buff (which may or may not be weaker when empowered)
Cunning Tactics is absolutely a must for poison-based builds. Every time it's off cooldown is 3-4 seconds you don't need to spend using Double Slash to get RNG Cunning procs for your Poison Blow. Over the course of a fight, especially a raid, this can save you several minutes of Double Slash attacks, and you can use that time for other things. Even at level 1, it's worth it.
I agree with your conclusion - the class at the moment has too many moving parts and too much RNG. It can't compete with other melee classes, and it certainly can't compete with the ranged DPS classes. Maybe this changes with the cap increase and future dungeons, but at least for the Fire Dragon raid I had to go in heavily on a Hasteless poison build in order to achieve anything, since the boss runs around all the time.