I remember those battles. Sometimes it was fun when the pubs could actually push back. However, most of the time it ended up standing at the turrets of the republic base, the sents/guardians would jump in sweep then run back to the base, the casters would get a cast off. If we were lucky a shadow would pull an imp to us only for him to be immediately eaten alive.
Very seldom was there an actual fight. I remember a few times we could push the imps back and those fights were somewhat fun. I guess what I'm getting at is most of the time it was a lot of standing around and like the video someone posted on the bridge there was 0 skill to do accomplish anything.