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LOL the problem with your argument is that you assume everyone is going to premix what they want to send ahead of time.

We live in the year 2016 and time is money.

72 hours to mix 1000 dash through DARKSEND isn't very impressive when there are alternatives that take a second or a few seconds.

Mixing Dash is actually very simple.

1) Sell Dash for XMR on Poloniex
2) Send XMR to own XMR address
3) Send XMR to a second XMR address with a mixin of say 5
4) Sell XMR for Dash on Shapeshift.io

Voila! Mixed Dash. No need to wait for weeks or worry about masternode blinding.

Edit: When sending the XMR to Shapeshift.io also use a mixin of say 5