AEMT's can do (depending on protocols, of course) everything that paramedics do on most ALS calls, and probably everything that has ever been proven to improve patient outcomes. Put the patient on a monitor / get an EKG, start an IV and give fluids, and give basic drugs like dextrose, narcan, epi, albuterol, etc. Where I grew up as a paramedic (western & central NYS) they also had intubation in their protocols, though they rarely if ever did it, and I personally wouldn't allow it if I were in charge of an EMS agency. These days with SGA's being so much better, hopefully they carry and are well trained on those.
I think well-trained AEMT's can be useful in the right system, you just have to use them appropriately. Their biggest limitation IMO isn't the skills that they can't do; it's their lack of education and (likely) experience with patient assessment as compared to your medics. On a critical call they should certainly be able to get things started (IV, EKG, etc) before the paramedic arrives, and then serve as the second medic.