I also have a MIDI Solutions T8 Thru Rack. So would I use the MOTU Fastlane interface and take the midi out from that, put it in the MIDI in of the T8 and then have all the MIDI out cables go to each of the respective synths?
Run a Fastlane out into your T8. Run the T8 outs to your instruments. If all are set to the correct MIDI channels, all will be good.
I entertained the idea of a Fastlane, it's a simple interface and if you don't have the MIDI equivalent of a LAN should be fine. It also comes in a range of colours, something that was rather important when presenting on "The Inventors" (as was "Is it safe for the kids?"). I like the transparent green, it would hi-lite my bright orange Microgranny 2. The MIO is white, the ME80P is cream, the MSB2+ is black as is that odd thing from the ABC and the V3. The Merge4 is brushed silver. I'm serious when I say I need more bright colours n my MIDI world. It's all too dull for something to do with music.

A midi interface will also help to prevent any ground loops. I noticed this with an Odyssey module using the low level output. Using DIN midi the signal was clean but with USB midi there was noise, not just noise but crackles, pops and whistles coming through the USB ground. The ground in a PC is notoriously noisy and as most synths are unbalanced (power supply ground = signal ground) this noise can and will leak through into the audio signal. DIN midi connections are optically isolated so there is no ground connection.
I use two Iconnectivity interfaces myself and all synths are connected using DIN midi, only controllers are connected via usb.
Good point about the ground loop. I've never had whistles and ricebubbles though, but I only plug-into a computer if I'm programming a controller or changing a routing rule.
I've had a second MIO on the list for awhile now, but like all musical gear that doesn't actually make sound, it keeps sliding down. Just the number of MIDI leads that can be removed by using the USB host is wonderful, besides all the routing and processing functions.