you’re right that dancing strikes is kind of a bad choice for a primary damage dealer. if you like how it feels however (i know i do), it’s worth keeping in your setup as a support skill to buff up your damage and defense. the “fighting arena” node is extremely useful, as are the “rhythm” branches, as long as you don’t mind weaving different attacks together.
multiple ailment builds are notoriously hard to make work since they scale off of different values. bleed damage has the highest default base value and poison has the lowest, which is probably why you see such a disparity between those values. the only reason you would ever go for multiple ailments in a build is for skills that deal higher damage per stack of ailment. rogue has a few variations on this idea. even if you were to go for this type of build, it’s generally easier to stack ailment chance for one type.
here’s a few ideas on where you could go with your build, depending on what you want to focus on:
ailments - drop shadow cascade, pick up flurry. pick up Alacrity, Relentless, Adrenaline rush (just 2 points for now, fill in more later), and whichever ailment branch you want to focus on (Festering Wounds or Bloodplay). poison has a much higher ceiling, but bleed is also very strong. the higher base damage of bleed means it will feel better with low investment. then head to the right side of the lower branches and get Vile Tactics and Lethal Vector (max this out for a nice damage boost), and again whichever of the 2 ailment branches you prefer.
if you want some range on the skill, you could opt to travel to the right side first, and (spending only as many points as necessary to travel there) pick up Shockwave. this will come at the expense of your ailment damage, but it might be worth it depending on how you like the feel of the skill with or without the shockwave.
stack %increased phys or %increased poison damage, attack speed, and ailment chance. don’t worry about your weapon’s base damage. dual daggers for poison, or sword and axe for bleed (because of the bonuses from Weapons of Choice on the blade dancer passive tree). dual sword can also work for bleed, since there are idols and gear affixes for bleed per sword. this variant can also be very defensive because of the glancing blows bonus for dual swords.
if you go poison, acid flask is good to keep around, especially with the poison pools. for bleed, i would probably swap this out for decoy as a better defensive option. the massive bleed chance while inside dancing strikes arena will be really nice as well.
hit damage with shadows - drop acid flask, pick up synchronized strike. rush the bottom right node that makes shadows use shadow cascade, then the top left for more shadows and shadow damage. i recommend getting the mana efficiency node (Dynamics) early as well, as this will help sustain the heavy mana cost along with the nodes i’ll recommend for shadow cascade below. for the rest of the tree, it’s up to you. i like the crit vulnerability node (Harmony of Death), although you can get more than enough crit vulnerability from the passive tree. crit vuln is MASSIVE because you can essentially ignore crit chance on your gear and focus entirely on damage, attack speed and crit multiplier.
spec shadow cascade into the nodes that refund mana per shadow and the crit chance/crit multi. this will use up a lot of your points, invest the others as you see fit. damage per shadow is a good one.
spec smoke bomb into the branches that generate shadows and dusk shrouds. again, maxing out those will take most of your points, so invest the others as you like. i like armor shred and slow.
either of the above variations without dancing strikes - if you don’t care for the more tactical approach of using DS to set up your other skills, you can drop it entirely.
decoy is an excellent addition to any build. the frailty and armor shred branch is very useful, and the taunt is actually kind of insane. i expect to see it get a little love tap with the nerf hammer, because it currently overrides the monster mod “focuses on attacking player” which usually ignores taunts from things like minions.
lethal mirage has a node that deals more damage per stack of ailment on the enemy, which can make it a pretty potent tool for bossing. it was actually broken for a while and had no cap on the amount it could give, but thanks to boardman’s 10 million (before nerf) DPS build it was quickly adjusted. 
Apprentice’s Corner also made a great crit flurry guide aimed at newer players. he tends to focus on Solo characters, which makes his guides very new player friendly, while boardman’s tend to be a bit more gear-intensive (of course they still work without perfect gear).
hope i haven’t overwhelmed you with info here. happy to answer any more questions you may have! 
