I agree with this, but have one gripe. Helping your teammate is good if you have captured any fuel and victory points in your sector. Once i have those defended by support teams i move up my tanks and infantry to flank the enemy in the other sector, preferably timed during one of my Buddy's frontal assaults. I also try to support my teammates with arty barrages and try to keep my mortars close enough to help them out. At least in a defensive battle. Every little bit helps.
In my experience it's better to continue pushing your side until you are in an enemy base. More than likely the other opponent will send forces to help push you back, splitting his firepower and his micro and making it much easier for your teammate to gain ground.
Don't know if ironic but IMO that is really the way to go. I HATE it when the other players think it's Facebook chat.
I'm being completely serious. Anyone who's ever seen me stream knows that this is exactly what I do