Lack of Web Engineering Tools

I'm a developer faced with a problem:

1. Web Applications which start simple grow into complex machines
2. Current UML & Software Engineering aren't that applicable to web apps
3. No community of developers appear to address these issues

I'm using the Cake framework for PHP , which is to a great extent:

1. Object Orientated
2. Scalable

However, when it comes the all critical planning stage , my team appears to have problems defining the problem area in sufficient detail to come up with an accurate solution.
Even worse , mis-communication of requirements can sometimes lead to applications which dont meet the clients requirements!
This maybe due to the fact that the team is still young and inexperienced with large-scale development .But the lack of proper Software Engineering techniques is a big factor in the current chaos when it comes to the Planning Stage.