That is pretty much the pain of getting that connection. The minute you see at Maidstone West the train is late by 3 mins you do pretty much accept that you wont get the Javelin eastbound at Strood. If you are on time you have to go through the gauntlet of the Strood subway asap to get to platform 1, and this isn't easy as there is often commuters that walk really slow to leave the station so it often means you have about 30s if you are lucky. You are even more lucky if the Javelin itself is delayed by a couple of minutes as it means your connection is easy.Very annoying as it causes it to miss the hourly down Javelin at SOO by a couple of minutes.
One thing that a lot of commuters don't realize is that your tickets are valid on the Javelin at Maidstone West in the morning if you need the NKML at Strood. The bad part is that there is often a wait of 15mins at Strood for anything Eastbound (I know 15mins is Peanuts for train waiting times but Strood isn't an interesting station) but seeming as the Electrostar service gets slightly busy until New Hythe, its not a bad way to start commuting in the morning as there is plenty of space on the Javelin.