Biass I would have to disagree with your assessment on UEF shields. They have the best combination of build time, bubble size, and shield health. The TMD does generally suck, but fortunately this isn't going to be a huge problem as UEF has the Ravager - which renders all T2 MML entirely useless. The UEF shields are more than enough to compensate for a lacklustre TMD, and for the early game, UEF TMD is good enough to get the job done.
The Ravager is hard countered by T3 MML and Artillery. In which case I recommend using the a TML. TML are excellent for taking out artillery.
As for the Triads. Yes they come at T2 and the ACU can't be everywhere. But UEF has one fundamental ability which no other faction has. It has the Sparky. The ACU cannot be everywhere - but Sparkies can. With this unit the UEF has the unique ability to quickly deploy T2 defensive structures anywhere on the map very quickly.