To be honest I still think that Urchin Underpass has some big flaws in it's design compared to other maps, although it's not nearly as bad as the original version. Right now, once the enemy reaches the path connecting the base to the middle it pretty much becomes a stalemate at best and one of the worst spawn camps in the game at worse, but they have to get to that corridor first. Previously all the enemy needed to do was push you off the middle and lob whatever weapons they had over the hill between the base and the middle while pushing/holding the side-path and keeping an eye on the small secondary corridor in front of the base. Guaranteed win right then and there. At least now you can try to keep the enemy at bay before they reach the Hot Gates, and the middle offers an interesting battlefield, but that's about it (we didn't even get to keep the tree by the base :()