There is indeed no need for --force-architecture anymore with multi-arch support with a some notes:
The libraries on which the package depend must support Multi-arch
Even if multi-arch is supported, it's possible for a library package to make the system install either the 32-bit version or the 64-bit one, but not both. So, the package in question should not have a need to depend on such a library unless there is no 64-bit equivalent necessary.
Many packages from third-party websites do not set the necessary dependencies. Before multi-arch, a dirty hack called ia32-libs was created. This would contain the 32-bit libraries for multiple packages, and therefore it was easy for the maintainer to say "just install the ia32-libs package." In most cases, the dependencies are mentioned for the 32-bit sysems, so you should install those, but for the 32-bit architecture by adding :i386 after each package as in: