Ya the tower we found in testing was generally best for a team to stack into, engis and all; if your prediction is sound you can flank around attackers coming up the steps by using the pipe route drop-down, or the other way around. There is an update that might come out sometime (valve time) that alters the map and gamemode a bit to make it more balanced, for instance making whichever team has the most points have double the respawn of the trailing-in-points team, to try to even out the scores, which I bet will help with annoying enemies.