Now that's a plan! Only trace I can think of would be outside of the crypto world, the connection to the VPN and Tor itself. And that's pretty much inaccessible.
Even then, i don't think there's a single point of failure... If Tor was to be compromised (unlikely), the second part of the routine would still protect your identity. If the VPN service was under governement controll, the first part would hide you... DASH is almost completely anonymous when using correct mixin value, most mixing services are not even known to the authorities, so there's no door to knock on,...
Also, using big exchanges for a short time seems more reliable than using 3 mixing services... Offcourse, mixing service, exchange and VPN provider have to be looked into before using them (just making sure there are no unsolved scam accusations against them, and their volume is OK)