Mixing in Monero is instantaneous.
Sure, there's a learning curve that goes with using the command line/terminal - but it's time well spent it if it saves you from having to wait hours every time you need to mix. And then you know how to use a command line/terminal!
Dash separated transaction mixing back in the summer of '14.
Initially it required mixing while sending, where you'd wait for others to mix and send.
Post-summer '14, it works with
premixing the coins (when you don't want to transact) so that when you want to transact later => it's instant / you are sending pre-mixed funds. It's a nice workaround.
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.