Surly the whole point of mixers are to work 1st time so i doubt you would need to use 3 differaent mixers which will cut down the risk you are exposing yourself too. 
ANd how do you know that the mixers dont log the transactions? Because they write on their websites? :-)
so regarding this point, that's exactly why I would want 3, because to find me, all 3 would have would to divulge which is unlikely if these companies don't want bad press on the street. If I used 1 mixer, then you are right, if they caved under pressure, then I'm screwed.
Now regarding the IP thing, I would use TOR but also access the internet when using the bitcoin stuff in public areas with wifi so can't be traced to my IP at home
Regarding the comment on bank account, now that I don't know. I'll ask my bank about that, but this isn't about paying taxes for me, I'm paying taxes, so not sure why they need to see from wallet 1, all they see is bitcoins into my bank, what's the big deal there?
now the casino comment was very interesting, i need to look into that more. so after 1 mixer, then deposit into casino, and then withdraw