Tomlin opened the scoring on 10 minutes before Assambalonga made it 2-0 on a 39th-minute lightning break. The on-loan Millwall striker then headed Southend into a 3-0 lead in the 44th minute and a minute after half time Tomlin doubled his tally with a clinical finish.
Sturrock said: "You have to give the front two credit, they ran them ragged. Their hold up play was good and they scrapped for everything.
"Gavin has got three in three now and is a great foil for Britt, who is an exciting player. I am glad to have Britt back on the score sheet because he was starting to worry me with all that superstitious stuff about what boots to wear.
"We are disappointed to concede a goal but we will take 4-1 away from home any day. We came to a very good side, they have got a system that works for them and they are very difficult to break down.
"But this team is beginning to gel and mould. It was frustrating at the start of the season because we couldn't get our hands on the right personnel. But now it is onwards and upwards. We don't see to have a problem against the teams above us."