They attacked the AGT! Without power the AGT is useless and as a target its pointless since it doesn't hamper GDI in the least. Anything else would have been worthwhile and more likely to succeed since the AGT is in the middle of the base where everyone can take shots at you.

As for the flame tanks, I'm "almost" in agreement they maybe too powerful. I rushed with 4 other people and we totaled GDI in 5 minutes. Everything.

However, on non-auto defense maps its not the flame tanks I'm worried about. Everytime I'm GDI I usually lose on those maps because of the stealth troopers and the nuke beacons.