On E'T....I have to be careful while we are attacking. I usually go south and get workshops/towers.....but every now and then there wont be enough horde to kill to rank up before the fortress is captured.
So, what i usually do every WG now(attacking or defending) is rank up as fast as possible then head south and do my thing. If a zerg wipes me out It is usually easy just to go and back cap the workshop they just left.

Or, just have fun 2-3 shotting sieges as they approach the fortress.